I think fans got so used to winning in the 70s-80s that when the downturn started, everyone aside from the diehards jumped ship. By 96, they were lucky to ever get 30K for a game. You see the same thing for the Steelers when they are having a sub-par season. The fans did come back to Pitt Stadium during and after the 97 season where we normally saw over 40K and sometimes 50K+ for the big games.
according to wikipedia, the next to the last game at pitt stadium against Miami only had 38k. I was there and that is probably close to being correct.