Well by the transcript of the Packers Thursday afternoon press conference it looks like the main reason is that Brett felt dis'ed and didn't think he could put all of himself back into the "awkward" return to the Packers. I'm sure that his agent didn't help as he is looking at the last year(s) of his star player and moving him could bump up his return. Inflating Bretts ego was easy, now he has to help Brett handle the hounds of NY. Good Luck Bus Cook, you'll need it.
In the end it came down to communication and timing. If this had all happened two months ago there may have been time to patch it up. The communication broke down because the Packers seem like they really never thought that Brett was really serious in coming back to play. And who would blame them as they have been down this road several times before. Brett and Bus the only ones to blame for that. If they were really serious earlier on they should have come to Green Bay and sat down face to face and set up the come back plans. Brett could have easily worked out in the Packers facility but did he want to? He said he didn't like the preparation and now he doesn't have to worry too much about training camp as preseason schedules have already kicked off. He can play and put up with the day to day in between. Good Luck Brett.