There was a lot of cruft about Song lacking application in training remember?
Personally I think it was a combination of all of the rumoured factors. Song's agent pushing his luck, Song getting cocky, Wenger having his usual desire to sell and feeling he had alternatives, and Wenger not being able to handle difficulties with his players beyond a certain point.
Conclusions: Wenger's judgement was off when he decided he had plausible alternatives, and he has shortcomings as a man manager. Song's a bit of a twat.
