The kind of people who voted for trump would never admit they made a mistake. They double down on stupidity instead.

That isn't true. There's actually a large number of people, probably in the millions, but probably not a majority of those who voted for him, who no longer support him in any way. And of the ones who remain, yes: they're pretty dense to still support him now. There are some lunatics who genuinely believe that the US has the right to dominate and exploit all other nations, but the majority of them simply believe the lies he's telling. I've already seen that when they are confronted with the facts about, say, Gaza, some of them can change their minds. It would be a mistake to turn them away instead of treating them like potential allies. There really is something more important at stake.

/r/LeopardsAteMyFace contains many counterexamples.

For better or worse, Donald Trump has absolutely earned his place in the history books. There will be so many lessons from this era, though I think it is very much open to debate what form those lessons will take and which ones will be the most consequential.