It is logically possible to approve of many things Trump has done, and even to have voted for him and to intend to vote for him again, while being clear-eyed about his grave faults. This is the transactional case for Trump that many conservatives have made. But some who made the transaction did not appreciate the full cost.
It turns out to be psychologically difficult to maintain the transactional stance. The temptation to minimize the flaws of one’s champion is too great. (It is of course also true that a politician’s opponents have the opposite temptation.) The pull of party unity is only stronger now that Trump is president — and has largely stuck with an agenda Republicans favored before he came along, while angering liberals every day.
Because our culture has defined racism as wholly unacceptable, very few people are willing to step forward and say, “The president keeps making racist comments, but what’s more important is that he is delivering on taxes and judges and regulation.” (Kris Kobach waffled rather than say it.) The evidence of his bigotry has to be ignored, wished away, re-interpreted. If Republicans refuse to fit their standards around the president — if, like former House Speaker Paul Ryan, they occasionally condemn the bigotry — it means they were weaklings all along.