I am having trouble matching this graph against other news sources. For example, here is an article from the Austin American Statesman.
Millions of Texans are experiencing a power outage. What energy sources contribute to the state's power grid?
www.statesman.com
Among other things, it states
As of Wednesday, 46,000 megawatts of generation were offline, with 185 generating plants tripped. ERCOT officials said 28,000 megawatts came from coal, gas and nuclear plants, and 18,000 megawatts were from solar and wind. (highlighting added)
According to your graph, the amount of energy from gas, coal, and nuclear combined increased during the crisis, as opposed to having dropped by 28,000 megawatts.
Also from the article
The issue became critical when several of the grid’s energy generation units began to go offline in rapid progression, affecting more than half of the grid's winter generating capacity, according to ERCOT Senior Director of System Operations Dan Woodfin. These failing sources largely included nuclear plants, coal plants and thermal energy generators. Frozen wind turbines were a factor, too, but Woodfin said wind shutdowns accounted for less than 13% of the outages.