When you have the majority, you get more attention from lobbyists and campaign contributors. But if you actually USE your majority against the Democrats, you get troubles.
The strategy, then, is to win, but then keep the Dems happy.
The major reason why the GOPE opposes Trump, is that he is unlikely to want to put up with that game.
Majority = Mandate!
If Trump wins in a landslide (which I fully expect him to) he will be given a mandate by the Majority Of Voters, and the UniParty schmucks will have no defense against the will of the people!
Go, Trump, GO!