You might stop to consider the evidence you offer to counter your thesis, that everyone who voted for Trump is a racist. As you say, many of them voted for Obama. As you say, that is not proof they harbor no racist sentiment. Neither does it disprove the idea they voted for Trump for racial reasons. In fact, I know several people who voted for Obama, and voted for Trump this time, and expressed racial resentment. So you may be largely correct, but there is no way to know for sure. When you look at an individual white Trump voter, you cannot know for sure if that person voted with racial motivation. Unless they tell you so, and some will.
Generally, I would say race played a larger role in this election than in the previous two elections for president. That seems odd, doesn't it? But I think many white voters trusted or liked Obama enough they were willing to overlook the fact he has dark skin. This time, they transferred some pent-up racial resentment, some lingering doubts about Obama, to Clinton. I get this idea from speaking with people I know who specifically cited programs to move black welfare mothers out of Philadelphia and Pittsburgh, and find them free housing in small Pennsylvania towns because the welfare benefits are more generous. There was also talk about Obama falsifying citizenship for Mexicans and ensuring they voted for Democrats. There were more conspiracy theories, of course, but these were the ones I heard repeated most often. It was as if some people had been storing up their racial grievances against Obama and dumped them on Clinton.
Of course, many white people voted for Obama because they knew he had a grip on things, and would not let the train go off the rails. I'm not sure why they didn't feel the same about Clinton, but I heard about lack of confidence that she would protect Social Security. That's an odd one, considering what Republicans want to do to the SS program.
I also heard some sentiment that the playing field had been tilted too far in favor of black people, that Obama had gone beyond the limits. I think this relates to your comment about BLM. Many white people expected Obama to calm things down, to marginalize BLM, something like that.