Question— if social democracies like Italy and Sweden etc worked remarkably well, why then has fascism taken root so fast and burgeoning even as we speak?

It seems to me fascism is inevitable in any society. Human nature is not altruistic.
Like children, we seek power and novelty. Is there such a thing as boredom with a system I wonder? We can be self-destructive; voting in people who we know are self-serving and ill equipped to be at the helm of democracy.