I think it was a lot of things, including some things that we don't know anything about, or haven't talked about, and maybe it's not really any of our business. He summed it up by saying that he didn't feel he had the energy level he used to, and he decided it was his time, which is a perfectly acceptable conclusion. If he wanted to express criticism or blame on anyone else for anything, he could have chosen to do that.
We all share a sadness to some degree that we don't all stay young forever. Also, an era of a team many of us found inspiration from and identified with may feel like it is fading away. I totally believe Sloan when he says he feels he's been blessed. Some eyes in the press conference looked a little teary, in thankfulness for the good memories, and the recognition that not all good things last forever.