The way I see it, making jokes about this kind of thing is a fundamentally human reaction. People often react to grim scenarios with humor, consider all the jokes about things like wars that exist- and being trapped in a failing submarine is a pretty grim thought that people might seek to distract themselves from by twisting it into humor. I don't think joking about an event like this that resulted in deaths is the same thing as wishing for people to die, they are, after all, already dead, and uncomfortable as the thought is, the dead are not as far as we can probably know capable of taking offense to anything. There is no possible harm that jokes or anything else can do to them anymore.

Obviously I would consider it pretty rude to joke about it around someone who knew one of the deceased, since you can at least cause emotional distress to those people, but I don't see a problem with joking about it on the general internet.

Another thing to consider is that some of the jokes have been mocking the quality of the sub itself, rather than the people on board (save for the ceo I guess). If you cheap out on stuff and that decision kills people, I think it's perfectly reasonable for people to mock you over it.