You are assuming Republicans are a stable and static population base and pool of people. If you look at the link I provided, the “Republicans” have lost people who have identified as such whereas Independents have grown. Being “Republican” Is no longer the same as what it once was. Trump helped to shift the Republicans more to the right. So, that smaller, more right-wing Republican Party could still vote him in.
But, here’s the problem with the Republicans: they are an aging white party. They are like the San Jose Sharks or Los Angeles Kings: they need a rebuild and to get younger but the GM is like “no, I have faith in my core of veterans”. If this was Canada, Trump would have been the guy to transform the Conservatives into the Reform party. How well did they do?
I’m just drawing a line between the Primaries and the General election. A shrinking party base can still vote their fearless leader as their 2024 nominee.