Racial Resentment is one part of it but I think the other part, which is more important, is that the Trump voters have been misled so long they don't know up from down.
A lot of well off Republicans have been completely duped into thinking the world is on fire. That foreign relations is awful. Do you know how many professionals have argued to me that the rest of the world looks down on us since Obama took over? That Europe doesn't like us now and he's ruined our great relationships?
Or that the economy is in the shitter. People literally arguing with me that the economy was better the day before he took office than right now. People who are convinced the ACA is an unmitigated disaster. That the UE rate is false and we're far worse off now than in 2008/2009/
Race relations is worse because of Obama, too. If not for him, we'd be better off. Oh, and the dirty poors get all this free stuff and are living the life while they struggle to pay the mortgage on a house they never should have bought.
These people have been told that if they just vote GOP, they'll solve it. They'll stop the ACA, improve the economy, etc. Meanwhile, as those GOP people keep losing, these people get frustrated with them. They're told they're "losing" at everything, everything is a mess, and now the people who promise to fix it, won't. Oh, and all this from someone who might not even be born here!
So they just moved on from one con man to another. And this one is different than the others because he's from the outside. And he has a "proven" record of winning.
The GOP, as a whole, has been a gigantic con since 2008. Okay, arguably before then, but it got turned up to 11. So these voters are predisposed to being duped.
it's not surprising that Trump won them over. These people are generally idiots. But they're idiots frustrated that the first set of buffoons that conned them didn't come through, so now they're onto the next one.
This is what happens when you intentionally keep your voters misled and uninformed to such an immense degree. Stare into the abyss long enough, yada yada.