Yes, it seems that lessons that could have been learned a decade ago were not. Here's a link to the FERC report on the 2011 outages:
Report on Outages and Curtailments During the Southwest Cold Weather Event of February 1-5, 2011
To be fair to ERCOT, it serves as an independent operator of the Texas electrical transmission system and coordinates the activities of the actual utilities and power plant operators in Texas. ERCOT can supposedly set reliability standards but its enforcement authority is weak.
I am sure you are right that maximizing profits entered into a lot of the decisions made, however electric utilities are very heavily regulated by state and local governments with rates set based on the cost of providing service rather than the market-based value of the service to the customer. The wiggle room for maximizing profits isn't that wide.
It is also fair to say that customers are generally in favor of keeping the prices they pay as low as possible.
The root of the problem IMHO is that everyone involved (including politicians and utility customers) hesitate to pay the "insurance premium" needed to protect against these rare (but inevitable) events; they would rather roll the dice and hope to stay lucky. Sometimes that works. Sometimes it doesn't.
15GW would be quite a big transmission link; very "mega". There isn't any location in the Western Interconnection with the supporting transmission lines to serve as an end point for that amount of power flow (and transmission in bordering New Mexico is especially meager). A better solution would be establishing several smaller transmission interconnections to the east, north, and west. I expect those would have to be HVDC for stability reasons. Or so I think...