As others have mentioned, the main reason Texas isn't trending more Democrat is because Hispanic voters are trending more Republican, which actually bodes well for the GOP's future prospects.
In general, the profile of Hispanic voters in Texas is increasingly looking more like that of the white, non-Hispanic portion of the electorate, and if current trends persist these two groups will eventually become largely indistinguishable. As a side note, these voters, as they increasingly move the GOP, are actually more likely to self-identify as MAGA and/or conservative than their white counterparts.
If the Democrats want to reestablish their dominance with Hispanic voters, the most likely way they can do so is through mass illegal immigration, and either waiting for the new arrival to become citizens and legal voters, or more likely just registering them to vote illegally like they do already.
Results from the two latest polls on the presidential race in Texas amongst Hispanic voters:
https://texaspolitics.utexas.edu/sites/texaspolitics.utexas.edu/files/202404_poll_crosstabs.pdfTrump +13 (5 way race)
Trump +12 (head to head w/Biden)
https://www.txhpf.org/wp-content/uploads/2024/04/TXHPFPresidentSenateApr2024.pdfTrump +4 (5 way race, note: TXHPF is a left-leaning organization)