No Bush performed solidly in TX. Reagan’s margins are completely irrelevant here because he nearly won a coast-to-coast landslide, whereas W won a squeaker in 2000 and a close race in 2004. Just look at TX’s margins before and after he was President and you’ll see that in 2000 & 2004 he got one of the biggest home state bumps in recent memory. This home state effect turned TX from a Likely R state into essentially a titanium R state on both the local and federal levels until the rise of Donald Trump.
1988: R+12.6
1992: R+3.4
1996: R+4.9
2000: R+21.3
2004: R+22.9
2008: R+11.8
2012: R+15.8
2016: R+9
And before 1994 Texas was just a Lean R state at best and at state level was a Lean D state and Bush basically obliterated the Texas Democratic Party for a generation . I mean Democrats have won state wide in Wyoming , Utah , Idaho , Oklahoma more recently than they have in Texas and that is all due to George W Bush .
I didn't question the state's PVI was solidly Republican in 2000. It just seems he did pretty weak in the metros given how popular he was and how notoriously regionalist Texans are. Maybe the gun issue capped his margin a bit? Then again, he seems to have overperformed in Austin, so who knows?