Are they being blackmailed?

That has always been my assumption as to why they affixed themselves lips-first to his asscheeks. As you said, he could be thrown overboard by the republican party at any time and like a month later Fox News would have conservatives worldwide convinced Trump had been a secret democrat the entire time, I'd never buy that they need him because of his stranglehold on their voterbase.

There's some sort of symbiotic relationship going on where it seems like the pieces to understand why it has to continue are unknown at present, but substantial enough that those who probably genuinely can't wait to see him gone and have the power to vote to that end are afraid of doing so.