Party loyalty. It doesn't matter that Donald Trump is Donald Trump. It matters that he's a Republican. The political parties in this country really whip their members up into a boiling mess, when the other party has a success, though the Democrats seem to be better at that, than the Republicans. George Bush sends soldiers to the Middle East, he's just trying to extract oil from the area, but a few years later, Barrack Obama sends soldiers to the Middle East, and no one says a damned thing, either because their own party did it first, or because now their party is doing it.
Case in point, you'll find that a lot of people were quite vocal about wanting Bernie Sanders over Hilary during the primaries, to the point of speaking out against Hilary. When the primaries were over, though, and Hilary was chosen as the Democrats' candidate, those same people turned around, and started chanting in favor of Hilary. There are exceptions to this, no doubt, but it's something I saw quite a bit of on Twitter during 2016.
Ultimately, who the candidate is, really isn't so important to people at large, even if they go out of their way to say things for or against that person. Which party they represent, on the other hand, is almost everything.