That shift came, I think, as the Marxists took over academia. The Marxists always tried to portray anyone to the right of them as some kind of fascists, because that is the only comparison they can make which might show Communism in a favorable light. So that is naturally how they redefined the political spectrum once they started teaching the political science classes.
Exactly, the Communists were able to take advantage of what Hitler did and threw around the term “Fascist” to condemn anyone who didn’t agree with them.
It’s why I say, “The only thing worse than a Fascist, is an Anti-Fascist.”