WW2 caused an aberration in American politics where fascism, and literal nazi’s, were shunned for generations. But there were violent anti-labor groups active in American prior to WW2. There were pro-Hitler rallies in America prior to the US entering WW2. Extreme right wingers have always been a part of American history. It just took 60 years for them to overcome the natural repugnance caused by WW2 and start openly proliferating again.
Imagine being a 25+ year career Republican who only has to worry about passing tax cuts to the rich, and suddenly these weird ass trailer park folk smelling of meth show up and they have total control over you. You step out of line? Primaried! Criticize trump? Believe it or not: Primaried! You now have to bend and grovel to illiterate conspiracy freaks. The republican party, folks.