You're confusing the election, which is largely a formality and political theater in dictatorships of capital, with the forces at play that have already decided who will take power. History is not a series of snapshots, but a process that develops dialectically over time.

Hitler was not elected, Hindenburg was, and he conceded power to Hitler. Trump was elected, but that's not why he gained power. Both gained power because that was what the capitalist class wanted, and the elections are largely a formality beyond that. Even if, say, Hillary had won, these two candidates are more similar than different, both were acceptable by capitalists, one merely preferred by some capitalists over the other.

Fascism rises when the spoils of imperialism dry up and reaction is brought homeward. It isn't a political preference, but driven economically, and as such is predictable. It has only ever been stopped through force, like when the Red Army defeated the Nazis in World War II.