People have agency.
You have a strange mix of the "great man" theory and the dialectic theory of how things work. The great man does a thing and people will automatically go down that course of action for decades because of dialectical reasons or whatever.
It's really the opposite. The great man can nudge things, but a lot of other people need to continue to make decisions to continue to push things in that direction. At any time people can decide "nah, I don't think things should continue to go in this direction." You should consider the reasons why a continuous push to fascism wasn't rejected instead of latching on to individual actions as being the one and only thing that made fascism inevitable.
The US has particular cultural issues that make them vulnerable to fascist manipulation. Racism is a big one. The mythology around the past greatness is another big one. There's also a general paranoia of government, and conspiracy theory culture. Reagan's little nudges here and there wouldn't have gone anywhere if there wasn't an environment for other's to continue to successfully push towards fascism.
You need to be careful in doing the thing where "Hitler was nice to his dog, so therefore being nice to dogs causes fascism."
Marxism teaches a religious prophecy where it's inevitable there will be a great cataclysm overthrowing capitalism which will inevitably become corrupt. It's not too dissimilar to the Christian revelations prophecies, probably why it's attractive for atheists that were previously in the Christian church. But the truth is, nothing is pre-determined, there is no such thing as "late stage capitalism", nobody really knows where things are heading, there are not mystical signs you can read to determine if a person is the anti-christ or fascist or whatever you want to label your ideology's demons.
Sometimes a cigar is just a cigar. Sometimes guy that says they want to lower taxes is a guy that just wants to lower taxes. That doesn't inevitably lead to an oppressive authoritarian state unless people go along with all of the other steps involved in implementing an authoritarian state.
And need I point out the fact that socialism has led to authoritarian states in the past? Does that mean we should reject all socialist policies out of hand?