Political Humor

It's actually pretty easily explainable as stupidity.

They don't actually know what being fascist entails, nor do they care to learn. They are told by conservative mouthpieces and their ilk that it means "Nazi" and they accept that as the definition.

They vehemently disagree with the idea that they're Nazis because the general belief is that Nazis are evil, and they don't think they're evil like the Nazis, and therefore aren't fascist. Even if some of them could see the parallels between their conservative nationalist beliefs and the Nazis, they would still argue they aren't and justify it with any excuse they could find. Human egos are self-preservationist, and it's in our nature for one to avoid viewing themselves as something they consider repulsive.

Uneducated/undereducated people who voted for him aren't cunning. They're just maliciously stupid, willfully ignorant, and easy to emotionally manipulate. That doesn't mean they're benign; in large numbers such as those enough to influence the outcome vote, they are an actual threat.

Beyond the stupid ones I mentioned above, there are the ones that willfully embrace fascism. The ones who wear "Nazi" like a badge of honor and take pride in their nationalist views. For them, I agree with you that they shouldn't be underestimated as merely stupid.