The situation is kind of amplified by the fact that they are now doing crew scheduling by hand -- their crew scheduling system went offline at some point during this fiasco -- and because they aren't a hub and spoke style of airline, they don't have flight attendants at their hubs...so, what's happening is that flight attendants are scheduled for a "leg" of a trip, from Altoona to Boston to Columbus to Dallas to Edison. This flight attendant will be on that plane from Altoona until they wrap up in Edison. Because of this interruption, they cancel the flight from Altoona to Boston. Now, they need to find a plane (and a crew) in Boston to fly the leg from Boston to Columbus...cascading failures throughout their system. Add in phone system failures, a winter storm, and the busiest travel week of the year, and you've got what Southwest has right now.
You have crew timing out, crews that are abandoned at stations, and some folks telling people to not expect their luggage for 30+ days. Southwest has also been delaying negotiating with their ground crew (it's been three+ years since they've had a contract), so, I'm almost certain that when they got the Denver "Operational Emergency" email on the 21st, most of them said screw it and quit: every other airline has struggled to hire experienced folks and my guess is that it won't be long until they're re-employed somewhere else
They've cancelled most flights until Friday, with the exception being flight for aircraft staging, and will struggle to find open seats for their flight attendants to ride on other airlines (even if they are flying space-positive) just so they can have crew at locations for flights.