from what I gathered, I believed that Israel just took some land on which other people were living ~70 years ago, displacing these people. Those peoples didn't like being displaced and tensions grew, until attacks happened on Israel, to which Israel had mixed responses with violence and suppression, rinse, repeat and escalate for decades.

Uh... You're forgetting the Apartheid, brutal military occupation, massacres, ethnic cleansing via settlers and every other injustice Palestinians have faced for the past 70 years.

Now Israel had it with attacks from Palestine

You do realize Israel is the occupier here, right? Setting aside whether Israel has a right to exist (it doesn't; Apartheid ethnostates have no place in the 21st century), they absolutely have no right to keep killing Palestinians and stealing their land, yet they've been doing it for more than 70 years.

and is going with the only chance it sees at maybe stopping it, which is a very violent war,

Even if that was true, collective punishment is a war crime and Israel cleared that bar even before they bombed half of Gaza into oblivion. Even if Israel's goals were justified, their conduct during this "war" is absolutely unacceptable.

at least if you accept the existence of Israel, because if not they are the aggressors for occupying the space in the first place.

At this point it's not a problem of "in the first place". Israel is an occupier because they keep militarily occupying Palestine. Gaza and the West Bank are still considered as militarily occupied by the UN.