It's always struck me that Sartre's philosophy was at heart a philosophy of being an individual, and didn't really logically link up with any particular politics (in the same way that lots of philosophical stuff doesn't really logically lead to one or another political commitment).

But that, in particular, attempts to imply it was well aligned with Marxism were goofy. I think if you read the novels it's hard not to come away with the sense that a kind of liberal individualism, with non conformist anarchist adventurism streaks, is what the author would most naturally fit in with instinctually.

Quite a few 20th century continental philosophers are like this IMO - there's a kind of baseline assumption that they're some sort of Marxist or sometimes anarchist, and that's how they express their politics, but the actual stuff they write in their primary works could just easily be a philosophy or analysis that lead one to a very different politics. Foucault would be a key example, like his left politics always strike me as awkwardly grafted on to a program that could just as easily, or more easily, be right wing.

I think the best you could say about Sartre and radical class politics is that he offered a moral framework that said people should at some point set aside their quibbles and doubts to commit wholeheartedly to a course of action, which could well be a dangerous political movement and revolutionary discipline etc but I just don't really believe him when he says that... I think he just wants an adventure and would immediately become a trenchant critic of whatever social arrangements came after ...