What got Southwest could get any airline: being stretched too thin, running schedules too tight, having everything just in time, all to cram as many fares into the sky as possible.
American also had huge delays and cancellations, United kind of always has huge delays and cancellations. There but for the grace goes any other airline in this situation.
The lesson from all this, it seems to me, is that if a meltdown can happen to a company like Southwest, which has ample resources and talent, then it could happen to anyone.