And the underlying causes weren't fixed.

Fascism rose a hundred years ago for precisely the same reason it does today.

The economy went to shit (Europe was in rags after WW1, with Germany, Austria and Hungary forced to pay restitution that led to reduced industrial and agricultural progress, meanwhile the US managed to jump from market crash to market crash to total global depression), and people felt like no matter what they did, there was no progress. Workers worked their arses off only to barely make ends meet, discontent was brewing, and elected officials were either intentionally blind to the issues or just completely castrated, unable to fix anything.

Which gave way to fascists. In the US, in the UK (which had a knock-on effect of mainland Europe being in the shitter economically, and the British Empire falling apart), in Germany, or Spain, or Italy, even in Russia. Fascists were able to pose as worker-friendly, national spirited solution-finders. Because that is what fascists do - cause complex problems, block any proper solutions, then come up with overly simplistic resolutions that the average people suck up (even if the experts say it's obviously not going to work), grab onto power, and not let it go.

It's literally the same shit happening again. All the issues of Europe - ineffective "progressive" leaders (in reality centrist pigs), US interventionism causing the immigrant crisis (not going to put blame on the individual immigrants, but one has to be blind to not see the knock-on effect of an already underperforming European market picking up tons of people who need shelter, food, amenities, and of course the ~30% tack-on economic migration and system abuse), all giving rise to fascism yet again.

Because again the altright is using the simplistic rhetoric of "if we get rid of [insert demonised minority here], all our problems will be gone". without addressing the underlying core causes of the current economic depression. And people suck it up because it's a simple answer, it plays into the tribalist spirit and shifts the need of critical thinking onto someone else.