I think a lot of people will point to democrats campaigning towards white suburban voters over black and brown voters. Which frankly might have been the right call, it would have been more of an uphill battle to flip TX and FL, though obviously the payoff would be way bigger.
TX becoming an actual battleground state bodes well for the democrats, though come 2022-2024 we'll probably be seeing a generally more moderate post-Trump GOP forming that will have better chances in TX.