It does not require single every Trump voter to prefer fascism, it only requires they either be ignorant of his true intentions or to not care, because as you say, they are selfish and think he will deliver what they want.
In my experience, a great many people are ignorant, selfish or both. What a lot of people who don't have much experience with Americans don't understand is that many people in America are racist to the core of their being. There are people in every society who have to step on somebody else to feel taller, and racism is the most important means by which they do so in America. As long as Trump gives their feelings official legitimacy, they will worship him because it makes them feel better about themselves. As long as he sticks it to the ones they have identified as the other, they really don't even care if he sticks it to them, just so long as he treats them worse.
I actually think Trump's appeal is much more about racism than it is about misogyny, which explains why so many women can forgive him for being a rapist. They are more afraid of men of colour they are of a white rapist and fascist. They see him as somebody who can stop these men from harming them and wiping out the white race. They believe this threat is real. This is a sad and horrible truth which even left wing pundits shy away from admitting, because then they'd have to face the prospect that America might be doomed as a democracy. Listening to Trumpers demonizing immigrants can impart this truth to you if you are willing to face it. The similarity to Nazi propaganda is uncanny, or for that matter, to the propaganda spread during the Rawandan genocide and every other genocide.
It's all; they're criminals, rapists, murderers, enemy aliens, enemies of the people, on and on and on. Trump even alluded to the Nazi blood libel, FFs, when he said these words;
(emphasis mine)
"They let — I think the real number is 15, 16 million people into our country. When they do that, we got a lot of work to do. They’re poisoning the blood of our country. That’s what they’ve done. They poison mental institutions and prisons all over the world, not just in South America, not just to three or four countries that we think about, but all over the world. They’re coming into our country from Africa, from Asia, all over the world.”
Note he only mentions continents where people are predominantly not white. Think that's an accident? It isn't. He knows his audience. He knows their fear and hate because he has those same feelings.
This is what he has very successfully tapped into.