The Dallas/Fort Worth area was hammered with thunderstorms last Friday. I was on their 8:30 departure from Houston to DFW. The aircraft came down from DFW and was 30 minutes late. Just as they were ready to board the FAA imposed a ground stop for DFW arrivals. The ground stop was extended hour by hour until early afternoon. When that happens all the airline can do is react. They can plan to have some aircraft arrive to send outbound but when the ground stop is extended that plan goes out the window. And after a few hours crews start running out of duty time. The 8:30 departure finally departed at 3pm. Driving home from the airport I ran into another line of storms with 50-60 mph winds that produced tornadoes south of Dallas. Some days were not meant for flying.
That being said, I don't think your experience would have been much different if you had been on Delta if Atlanta was shutdown or United if Chicago was closed.