The population of Texas increased by 4 million between the 2010 and the 2020 censuses.
That's about 400,000 per year.
So, between 2016 and 2020, the Texas population increased about 1.6 million [give or take].
Joe Biden got 1.36 million more votes than Hillary! in 2016, while President Trump got 1.19 million more votes in 2020 in Texas than he did in 2016.
While Trump was increasing his popularity in Texas, Jao Xiden was scooping up ALL the influx of voters from 2016 to 2020, plus hundreds of thousands more.
Neat trick.
1.36 + 1.19 >> 1.6
The story seems to be more than a bit complicated.