De-Stalinization undertaken by Khruschev was basically the starting point for everything going wrong. Not that mistakes weren't made prior to this, or that the SU wasn't able to accomplish great things after it, but the trend line across Soviet history where Marxism becomes less important as a guiding ideology and the people and the party leaders' desires begin to diverge from each other starts descending there. As Xi Jinpeng puts it:

Why did the Soviet Union disintegrate? Why did the Communist Party of the Soviet Union fall to pieces? An important reason is that in the ideological domain, competition is fierce! To completely repudiate the historical experience of the Soviet Union, to repudiate the history of the CPSU, to repudiate Lenin, to repudiate Stalin was to wreck chaos in Soviet ideology and engage in historical nihilism. It caused Party organizations at all levels to have barely any function whatsoever. It robbed the Party of its leadership of the military. In the end the CPSU—as great a Party as it was—scattered like a flock of frightened beasts! The Soviet Union—as great a country as it was—shattered into a dozen pieces. This is a lesson from the past!

Putin has mentioned that there were CIA agents in Russian government in the 90s.

Most of the stuff pointed out (cultural conservatism, bourgeois "rights") are liberal posthoc stories told by the west as cover. The soviet union failed plain and simple because the party itself did not believe it was legitimate. Economic dysfunction is not an automatic death sentence for a regime, otherwise the high inflation and chronic shortage nations like Argentina and Mexico would have their nation states fragmented and replaced every few years.

The USSR, starting with Khrushchev as ssjmarx puts it, was run by a vanguard party that shit all over its past leaders and embraced nothing but personal gain and bureaucratic ladder climbing. By the time you get to 1980s USSR, the CPSU was not a party of the people but a party over the people.

In fact, Gorbachev's glastnost policies were the impetus for the west to seize upon nationalist movements in undermining the USSR. The state security apparatus that had kept the union together for decades suddenly couldn't act on nationalist sentiment. And once people got used to complaining about the CPSU it was pretty much all over. Opportunists inside the party and all over worked overtime to heighten every crisis . Ultimately, you can trace the start of the collapse to Gorby flying to Crimea to renegotiate the Union treaty into something more like federalism, but by then Union hardliners had enough. They couped him and in the resulting chaos opportunists like Yeltsin were able to seize the initiative and dismantle the USSR republic by republic.

Another thing that ties with most other points is that , by little choice of its own and due to cold war shennanigans, the USSR for decades even afterWWII spend a good 20-25%+ of their GDP on the military and intelligence operations. Thats a huge handicap to have for a country with their starting material conditions that went through a devestation such as WWII and limited the wiggle room they had domesticaly for more treats to the citizens and in general more whole scale departure from exploitation and overtaking the west in many cultural and economical ereas

So, it was a near run thing. As late as early 1991 it could probably have been saved (I don't hold much chance of the August coup succeeding.

• The people were old and there were some issues with turning things over, but the next generation of potential leaders were often those who were the worst looters.

Also, they were not that old despite the memes, Biden is older than every Soviet leader when they got into power. He's nearly older than every leader when they died! (Gorby is the exception) Andropov was 69 which is old, but not unheard of even in nations where Leaders are traditionally in their 40s when attaining power (Churchill was 66 I think in 1940 and people thought him too old for power.)

• I would not go as far as calling the Nomenklatura a new class. They were not and people drastically underestimate the power workplace councils and local Soviets had in the SU due to Great Man theory and CIA propaganda. But yes, the Beauracratisation of the SU was an issue, one that Lenin precipitated, Stalin made worse before realising his mistake, and almost every leader tried and failed to solve. It is one of the reasons the SU could not reform.

• The S-S split is a tragedy, and if it didn't happen yes, the SU would be here still. It's a serious lesson in Left Unity, and the reason I always support states like the DPRK that I otherwise might strongly critique. We cannot afford bullshit like that ever again.

• Cultural Conservatism waxed and waned, though it is something to critique. I might note that a lack of it didn't help the GDR

• This gets close to the major cause, but the USSR was exposed to bourgeois subversion. If everyone had believed in the system, the USSR would have pushed through what was a far less serious crisis than that of it's first 30 years. Many useful reforms could have been made. But after Stalin's democratisation measures were repeatedly voted down and Corn Pop cemented rule of the party nomenklatura, its hard to see how more power could be devolved to local Soviets. China has made great strides in solving this. IMO, Cuba and Vietnam have done even better.

• The wealth gap was a huge issue in the 80s, mostly because the SU decide it was. But it was primarily an issue in the upper ranks, who basically dissolved the SU for treats.

• Gorby did kill the SU through about 5-6 consecutive bad decisions and yeah, tactically, he's the precipitator of the fall.

I'd like to add a reason of my own

• The underdeveloped nature of the Soviet Bloc. Only Czechoslovakia and the GDR could be considered fully developed as economies, and both had been wrecked and looted, first by WW2, then by Nazis fleeing west with half the factories, then by Soviet reparations. The SU was largely Feudal in 1917 and despite mistakes their modernisation of the economy was far, far less bloody than the famines and clearances that accompanied Capitalist development. Despite this, the Soviet Union never quite managed to complete industrialisation in many areas beyond an 1850s-style primary resource economy (with modern bells) At it's peak just before the Sino-Soviet Split, the entire Communist World had a third to a half of the economic power of the USA. China today is more powerful economically than every other socialist state, living or dead, combined.

• Following on from this is the fact that market socialism is hard to do, you either have an NEP/Dengism and let some billionaires in and hope they don't slip the leash, or you do a full command economy, which in the 70s meant you could only command about 100 products, and that not well. Everything else was just kind of half-assed between quotas from stats agencies and an informal fixer arrangement. The SU, assuming it doesn't continue the NEP into the 1930s, made two horribly poor decisions here. One was to not cybernetise the economy and develop an internet in the 60s. The second was to implement market reforms at the exact fucking moment command economies that controlled most primary and secondary industries became possible. The SU literally marketised its internal industries just as the People's Republic of Walmart was swallowing up its suppliers and vertically integrating its logistics.

• Seige Socialism: After the failure of the Rhur Uprising and the Soviet defeat at Warsaw, the Soviet Union can be seen as a state under a slow, strangling siege from the west. This never stopped, and since the west out-competed them economically, it was only a matter of time before one crisis or another killed it, or it managed to achieve command economy take-off and out-compete the west. China has taken the road of the NEP, and looks like it could probably start integrating it's primary industries entirely! Xi is making some moves in this direction, though not as many as I'd like.

First line of Capital by Karl Marx : "The wealth of those societies in which the capitalist mode of production prevails, presents itself as “an immense accumulation of commodities""

Average life of worker under capitalism - Work, make wages, buy stuff with wages, repeat.

Average life of worker under USSR - Work, make wages, buy stuff with wages, repeat.

It is this condition of the working class that communists seek to abolish. The working class in USSR suffered the same impersonal domination of the value-form as working classes everywhere.

The USSR could not be communist because communism is an international movement, not something that can be realized in a single nation. Look at any capitalist country, trade(exports and imports) makes up a giant chunk of the GDP.

The USSR called itself communist because since the Stalinist counterrevolution, they were simply opportunists who seek to enforce their own different version of capitalism while pretending they were communists (ring a bell? China, Cuba, NK all do the same thing)

Communism is the real movement of the working class to abolish their present conditions of existence, and replace it with one where there is no longer any domination of capital over man, nor is there domination of man over capital, but capital literally doesn't exist anymore.

There is no money, exchange, wage labor, commodity production, profit and other such categories in a communist society.

Such a society can only be achieved by an international movement of a revolutionary working class led by a class party that follows the principles of scientific socialism(aka Marxism).

Hope this is clear. If you want to understand more, read the following texts

"Communist Manifesto" by Marx, "German Ideology" by Marx. And these following ICP party texts.

https://www.marxists.org/archive/bordiga/works/1958/marxism-property.htm

https://www.marxists.org/archive/bordiga/works/1957/fundamentals.htm https://www.marxists.org/archive/bordiga/works/1926/lyons-theses.htm. If you spend the time and effort to understand these 5 texts, (it will take 6 hours at most) you will already be a better communist than 99% of self described communists out there, online and IRL, who simply do not understand the basic concepts of what communism is and what actually has to be done.