I would hope that other Republican candidates for the nomination don't purposefully alienate general election voters, including the Jeb Bushes of the GOP. Given a choice, the Jeb Bush Republicans generally would rather vote for a small government conservative than for a second round of Biden. Now granted, that doesn't really describe Trump, and most of them don't like Trump. So at this point, he can't really alienate them further. But those should be easily winnable votes for other GOP candidates as long as they don't deliberately alienate those voters.
The dynamics of the 1980 election are clearly in play here. There was a very definite split in the GOP - and some bitterness - coming out of the 1976 primary between Reaganites and the moderate GOP old guard led by GHWB, and it carried over into the 1980 primaries. There were significant differences in policies, messaging, etc., that are somewhat similar to the divisions in the GOP we see today. But Reagan never went the "Us v. Them" route. After winning the primaries, he brought them into the larger GOP tent without compromising on his own views. And they were willing to support Reagan because even thought they didn't agree with him on every issue, they were much closer to him than to Carter and the Democrats overall.
The fact that those moderate Republicans were willing to support Reagan in 1980 wasn't evidence that Reagan compromised/was compromised. It was evidence that the Bush wing compromised. And that's exactly what would be happening if the (Jeb) Bush wing lined up behind conservative alternatives to Trump. It doesn't mean those candidates -- Pompeo, DeSantis, or whomever -- are compromised. It would mean that the Jeb Bushes have compromised.
You win elections by winning more votes in enough states than your election opponent. A juvenile "us v. them" mentality that makes an enemy out of everyone who doesn't line up with you on every issue is simply foolish, and self-defeating.