I was in grad school at the time. I remember thinking he'd get us back to prominence, and get us out of the 5-11 gutter we'd fallen into. I was hopeful, but I wasn't predicting Super Bowls. I remember wondering how much he had left in the tank. Turned out he had about a year and a half.
I just think he was too old and too long in the tooth to be able to deal with the negative aspects of the game (losing, travelling, endless days, high drama players, etc)
There's always more to the story.