Southwest didn’t spend “too much of their profits on stock buybacks”; the only airline that did was American and it’s a kind of tired refrain to blame all the airline industry’s problems on something one CEO did.
This catastrophe was Southwest not investing enough into modernizing their computer systems. It caused their staffing system to crash when the storm cancelled so many flights nationwide and there were so many staff members stuck somewhere they weren’t supposed to be, and therefore unable to fly their next leg. So many staff members trying to adjust their schedule at once crashed everything, and Southwest basically needed to just cancel most flights for a few days, “reset” everything, and only fly the flights that were important to get staff back to where they needed to be. If that hadn’t happened, they’d have had plenty of staff on hand to handle baggage. Of course the nationwide storm hitting their two biggest hubs (Denver & Chicago), their use of the point-to-point system instead of hub-and-spoke, and the usual Christmas rush all exacerbated the problem and weren’t Southwest’s “fault”, but most of the blame here falls on the failure to modernize software, not stock buybacks.