Actually it makes it almost a complete exception to the rule of states that vote Republican.
Reiterating your post doesn't make it any less awful. Using your logic, Vermont should be a solid Republican state because RURALS.
...and no one in their right mind would call Vermont the "Heart and Soul" of the Democratic Party.
Just like no one should call Texas the "Heart and Soul" of the Republican Party.
It's not that complicated here.
Texas is socially conservative, has a very conservative suburban AND rural population, is a very religious state, has a good chunk of wealthy Whites and has a large business community. Whether you like it or not, all of those represent a very significant faction of the GOP, pal.
Wealth isn't a good indicator of being Republican or Democratic. Texas is more Urban than the country as a whole, and has some of the biggest cities in the country.
The only thing you really have there is the religious part, but that alone isn't enough.