I think the party machine has known for a wile he is a liability. But the base are so hooked that its more of a cult than a traditional party. The donors and establishment types might want to move away from him but that would come at a cost.
Trump won't quit and he will drag them down with him. I think they know it but what can they do. They allowed him to turn it into a personality cult. If they were smart they would have impeached him after Jan 6th. They did not and they have to live with it.
Mitch should have convicted him in the Senste and now they are paying for it.