> So basically, this is the worst winter in the history of Texas to such an extent that nobody could have possibly predicted this?
It's a bad winter, but not "nobody could have possibly predicted this" bad. Some cities are breaking records, but quite a few haven't. For example Austin's Tuesday low of 7F is cold, but not quite as low as the record from December 23rd 1989 (6F). San Antonio recently tied their all time low from December 22nd 1990. Obviously "coldest winter in 30 years" is quite the statement, but it's still well within living memory and not the distant past. Chances are most of the policy makers and system designers for the TX energy system personally remember the winters of 1989 and 1990.
There's also a 2011 report recommending that TX winterize its power systems in case this exact thing happened. So at least back in 2011 energy experts saw this as a distinct possibility.