Obviously could've handled the situation better and been more honest with the faithful, but at the end of the day a person can change jobs if they want to. Accepting jobs in larger, more successful programs is par for the course - and besides, if his heart isn't 100% in it, it's better to let him walk now than to waste another year.
Also, the 7-5 record isn't so bad considering the problems and team he inherited from others (like Chip Kelly).
Better luck next year.