1989, 2003, 2011, and now 2021, I don't think I'd call this a once-in-30-years event. When the Federal Energy Regulatory Commission released a report[0] after the Feb 2011 hard freeze, they said "While extreme cold weather events are obviously not as common in the Southwest as elsewhere, they do occur every few years," which seems to have been bang-on.

That report, like this article, correctly identifies ERCOT's "energy-only market" as the underlying source of problems, in my opinion.

0. https://www.ferc.gov/sites/default/files/2020-04/08-16-11-re...