The issue has only really came out recently that Trump has no idea what he's talking about and is a liability.
No, I think everyone knew; we all did. But thought they could puppet him like Putin has.
I think how it came about was that their candidates were not strong. They wanted back into the white house and Trump seemed to offer a lot of the old school business/cult votes and had a plan to get the votes of all the hicks and idiots and also have some "Help" from "Friends" Abroad.
With that he both fooled, cheated and bought his way into the white house.
Note: For years now, every time Republicans have got power they have continued to put laws in place to protect themselves and the president despite how corrupt they are. They are also always running their process to make themselves and their rich friends richer. Always undoing laws regardless of their good, putting new ones in place etc.
They got Trump his seat and hoped they could control him and I think they knew he was an idiot and crazy but hoped that they could still control him. Over time though it became clear that he liked the power and that he was more of an idiot and loon than they realised.
He has done all he has done and they have desperately tried to fan the flames he has created while anyone that went "Oh crap we made a mistake" has been quickly and brutally dumped, shuttered etc.
It has got to the point that they have spent so much time lining their pockets and fixing/covering up/ managing Trump that they have no one in their party that could have the public viewing to replace him. It is all they have got at this point and they got to run with it.
Right now they are loosing all their seats left right and centre as a result, they are in a real mess and I think they have little or no ability to really fix it but to ride the Trump bull crap train to try and get it to work again for the next election.
I think when the next election comes, unless there is really dodgy stuff going on and America is not a total lost cause - they should loose. I
do not think the republicans will be in a good state after this and it will take them some time to recover. I think it will be 8 years before they get their next shot.