This is an excerpt from a HuffPo article that is well worth reading as it lays out how the Repub leadership knew who Trump was and is. It's written by a man named Jeffery Young and is worth reading in it's entirety. For rank partisan reasons the GOP leadership put the interests of their party above the welfare of the nation. They knew who Trump was  because they created him:

"You knew he waged a racist campaign against the president’s legitimacy. You knew he called immigrants rapists. You knew he advocated forbidding Muslims from American soil. You knew he said a federal judge wasn’t qualified because Mexican blood flowed through his veins. You knew he besmirched the parents of a dead soldier. You knew he mocked prisoners of war. You knew he courted white supremacists. You knew he admires dictators. You knew he incited violence. You knew he lies ― blatantly, shamelessly, ceaselessly.

You knew all of that, and you asked Americans to elect him president anyway. Shame on you. You knew."