Bush is a good definition of center-right. And for conservatives, that is generally an acceptable place. For example, he screwed the pooch on CFR, hoping that the SCOTUS would defang it, but he also realizes the mistake and has not championed further infringements on the 1st amendment, like McCain. For every cringe moment we get with Bush, we can take comfort in his other strengths, where he has furthered Reagan’s vision.
But moving from a center right GOP president to a center-left one makes ZERO political or practical sense. One can reasonably argue that Rudy is better than Hillary (he is) but no one can argue that Rudy is good for the conservative movement or the GOP’s standing as a conservative party. Hence the need to undercut him now.
In a nut shell, you nailed it.