It's not. You need to look at more than just PVI to understand local election dynamics.
No, I’m very much aware of local election dynamics and I’m not just looking at PVI. However, I’m also aware of how Beshear was
actually able to forge a path to victory in KY, which was by (1) massively outperforming previous Democratic candidates for federal
and statewide office in urban KY not just in terms of raw votes and turnout but actual percentage of the vote, (2) dramatically outperforming Clinton and pretty much every recent Democratic candidate for statewide/federal office in the historically Republican suburban/exurban areas of the state, (3) holding his own or only losing a little ground in the state's rural areas, and (4) benefiting from the fact that enough Trump supporters stayed home in an off-year election, not least due to Bevin's unpopularity. There’s really no way Beshear wouldn’t have been able to replicate this path against a Republican as unpopular, incompetent, and odious as Bevin in GA/TX (and arguably even SC), where Republicans are even more reliant on suburban and (especially in the case of TX) urban support primarily but not solely(!) from college-educated voters and to a lesser extent non-white voters to be competitive statewide. These voters might not have a determining influence on the outcome of a KY election, but they sure do have enough influence in TX and GA to give a Bevin-type Republican the boot. Factors (1) + (2) + (4) would have been in Beshear's favor in TX/GA/SC too (this isn’t really arguable either), and arguably factor (3) would have been in his favor too considering the weird turnout dynamics in off-year elections and Collier's very respectable showing in rural TX last year.
The premise of your argument is that Beshear's victory was solely due to the revival of some conservadem/Dixiecrat/rural populist coalition unique to the Upper South/Clinton 1996 states, but that’s not really true and hardly tells the whole story. Sure, Beshear would have lost KY with less rural support, but he could have afforded to do a lot worse in rural GA and TX simply because the demographics of those states are infintely more favorable to Democrats than in a state like KY or TN at pretty much every level, and he almost certainly would have lost in AR for similar reasons too. This isn’t 1980.
