The true answer is that political fringes have always attracted neurodivergent people. Mussolini was a former Marxist. I have known an anarcho-communist who became a fascist then back again, and is now an apolitical hermit.
"Normal" people, "normies", even yes the dread N-P-C term tend to have ideologies that tweak the status quo. Imagine the absolute chaotic hell out world would be if everyone was deep, intelligent, and abstract and had a special ideology. "Sheeple" are a basic requirement for a stable civilization. I mean absolutely negative by that of course. I wish I didn't have autism for example.
Extremists will always be extreme because they have different brains that is why they can flip ostensibly different sides so well.