Sometimes I think Republican leaders are putting party before Country. Sometimes I think they believe that weathering the storm of Trump is better for the Country than the trauma of the ugly truth being exposed. Sometimes I think the latter is used as a rationalization for the former.
Either way, I don't hold the belief that very many people who actually work with Trump on a daily basis think he is remotely fit for office. I do think he had true believes (e.g. Cohen) under his spell when he was a private businessman as he had unlimited capacity to dictate at the time and had virtually no constraints on what he could dictate.