system
Given the following post, respond as if you're commenting on Reddit:
human
How does existentialism and communism fit together?

The most prominent french existentialists I have found were communists—Camus, Sartre, De Beauvoir. I think even Che Guevara might of been an existentialist too.

I'm aware that Heidegger was Nazi, and Nietzsche was co-opted by them.

Is it just that both existentialism and communism came to prominence similar time? I really am not sure.
gpt
It might have to do with the fact that Existentialism, in general, tends to present the relative independence of the individual from the conventions of larger society as an ideal. This means that existentialists are probably more likely than other people to embrace political programs that advocate for the radical transformation of the social structure, and less likely to take positions that argue that we need to preserve the status quo. It's also the case that Marxism and Existentialism, in general, share the view that in some sense "human nature" isn't fixed, and that it's always capable of being transformed (for Existentialists, usually through some sort of individual choice, and for Marxists, through a change in material conditions and relations of production) so there's at least some sort of *prima facie* metaphysical connection between the two schools of thought. That said, you can't really fully answer the question of why any particular Existentialist thinker was a communist without engaging with that thinker's work on the subject. Historical generalizations can, at best, only tell part of the story.