I think there are other factors here. UAL, like all the majors, went to the "Hub" concept years ago. It looked good on the drawing board. Management was very happy with the efficiency of it all.
PAX were not. Many hubs became nightmares. DFW, ATL, and STL are a few that come to mind. Endless walking through crowded terminals trying to catch a minimum time connection is no way to attract travellers.
The point-to-point way is the way most PAX prefer to travel. Southwest and Jet Blue use it, as if it was a "new" concept, and they make money.
Then there is the ridiculous security checks. Frustrating to the point that many PAX would rather stay home.
United had a nice station in Stapleton Int'l.. Just minutes from Downtown. Somebody decided it was all wrong, closed it, and opened a nightmare of a hub way out in the Colorado prarie.
TWA did the same thing in Kansas City, only worse.
Of course, we can go way back to that nightmare legislation called "De-Reg."
Put it all together, and you have a dissaster.