The GOP has tolerated him because they want to take down ACA and cut taxes as much as possible, knowing that the longer this disaster goes on the less of a chance they have of keeping majority...
Now they have the option of taking down Trump and possibly saving face by blaming all of it on him but if they do it before ACA is gone this is a net loss for them.
If on the other hand they stall for too long and Trump does something that even the GOP does not tolerate (normally I would say something like what he just did but seeing the stuff they have already ignored I don't know if there is any treason or incompetence that is too much for them) and some of them join in with the Democrats they lose face and can't defend themselves by making a show of stopping Trump.
...Or if the Democrats/voters manage to impeach (or whatever they can do to him) Trump without help from GOP AND it happens before ACA -and whatever else they are after- have been destroyed they have lost it all for nothing.