Why did they fail? Obviously, famine, wars, etc had a part; but as the saying goes:
Hard times create strong men.
Strong men create good times.
Good times create weak men.
Weak men create hard times.
I do agree with your broader point though that it's worth asking if society is getting more illiberal and intolerant of opposing views. It's not just a "young people these days" kind of thing.
https://acoup.blog/2020/01/17/collections-the-fremen-mirage-...
That saying is ahistorical and Bret goes to great lengths to show where it fails.
Fascists seen empathy and niceness as weakness and something bad. They were also something that emerged from hard times and created misery and pain. Lets not promote their ideology.
The German people after World War I were suffering. Significant reparation burdens had been placed upon them. They were starving and angry. These should have been the "hard times that create strong men," yes?
It created the Nazis and they were defeated militarily. Seems something went off in step 2 there; nobody considers Germany during World War II "Good times."