The fact that extensive load shedding and brownouts etc needed to happen was not a result of decisions made during the weather event, but lack of infrastructure investment over decades (that may or may not have been under the control of ERCOT, rather than the legislature and state government regulators, but ERCOT certainly was on board with/lobbying for the conditions of deregulation that led to them).
During the weather event... ERCOT, the grid operator, did their job very competently. Making more capacity come online or reducing consumer demand was not really something that could be done during the weather event. They kept the grid from collapsing -- and it nearly did collapse, it was a close call. That was their job during the event.