From CNN:

Texas produces more power than any other state. Here’s why it went dark anyway

Short answer: to avoid federal regulation. How’s that working out for Texans? From KXAN.

Why does Texas have its own power grid?

Can’t ever recall weather like this in this part of the world. Been below freezing for days. Here we are, snowed in during a pandemic. On Mardi Gras. 2021, I had such high hopes for you. If we are being honest with each other I have to say it has been a bit of a disappointment so far.