Root cause seems to point towards prioritizing shareholder value over providing services, and lack of regulation enabled by Texas laissez-faire handling of utility providers.
A short timeline: In 2014 CNP reported ‘excess revenue’ but were allowed to keep it https://stateimpact.npr.org/texas/2014/10/20/texas-puc-leave....
In 2020 a major activist investor put a large stake in CNP https://www.bizjournals.com/houston/news/2015/12/14/billiona.... The owner of that private equity group also happens to be a major donor to the political party of the current Texas governor, who appoints the commissioners who regulate public utilities (https://theintercept.com/2020/10/15/paul-singer-hedge-fund-r...).
Texas electric utilities are regulated in theory, but in practice this regulation seems lax or at least not proactive. This was readily apparent in the 2021 freeze (Uri): https://www.statesman.com/story/business/2021/10/21/texas-re...
And later in 2021 CNP also made direct political donations to Texas politicians: https://www.texastribune.org/2021/08/04/texas-energy-industr....
It doesn’t seem like Texas has done much to improve regulation since the 2021 failure. https://www.tpr.org/environment/2022-11-17/texas-lawmakers-a...
https://www.newyorker.com/news/letter-from-the-southwest/why...
It’s hard to see how these apparent conflicts of interest (and lack of regulation or consequences) don’t create an environment where a state supported monopoly can abuse their position by putting short term profits first.