I’m speaking more practical outcome rather than what a specific player like Sasse might be trying to do with his actions. Doing the right thing for the wrong reasons.
Overall this sort of thing works to Conservatives advantage. Trump is building and riding a movement that’s independent of the GOP apparatus. This sort of thing only helps him with his supporters. But allowing downticket candidates the independence to run towards him or away from them, even fostering their ability to do so, based on the particular circumstances of their voters, will help save many threatened downticket seats.
It is amazing how some folks seem unable to set aside their emotions and see the clear logic of what you're saying.
A senate in which Chuck Schumer is running things is going to be worse for any GOP Presidential nominee than a Senate run by McConnell. The time to "primary" Senators who aren't sufficiently conservative is during the primaries, not during the general election.