We know a significant share of Republican voters are openly racist and Trump probably did very well in that demographic.
The point with Trump is that there is little to no reason to support him beyond shades of racism and fascism. He's not offering solutions to any problems, no coherent ideology or principled conservatism. He doesn't stand for family values, a secure and strong America, free markets or small government.
Anyone enthusiastically supporting him must care about something other than all those things and it's hard to escape the conclusion that it is the one thing he does champion in a unique way - racial hatred and persecution of non-white minorities.
To be fair to
TrumpMiller, he's also doing a good job carrying the anti-science, pro-ignorance banner at the front of the GOP parade. (That's not a completely overlapping set with racism and bigotry.)