Economic and social collapse dislocates a lot of people. It dislocates people who think they shouldn’t be dislocated, because they played by the rules. They go to church, they had a job, they’re patriotic to their best understanding of the word.
Then, in their minds, something must have changed. It might be the immigrants, or the Jews, or the gays, or weirdly drag queens for some reason this time around. Then someone comes along who validates them as victims and promises a return to their historical glory days.
The last paroxysm is the election or ascendency of a far right populist who elevates that narrative. They promise to restore national pride and return to traditional values, and to return the nation to its roots which had made it strong and put them on top.
It’s happened multiple times around the world, and there are a lot of books and articles on how and why it happens.
but it’s also marks the end of capitalism and what comes after.
No, it doesn't. Fascism poses no threat to capitalism and never has - that's the whole reason capitalists eagerly fund fascists into power. Some fascists might dislike capitalism - such as Franco, for instance - but that doesn't mean fascism can exist without it in any way, shape or form.
Oh you got me wrong, of course fascism is created to serve capitalists, but after the fascist power grab, they don't need to have the theatre of freedom™ and markets anymore.