The reason Di Matteo's announcement of being made full time manager was delayed for so long last season is that Mourinho was on the verge of signing a contract in the summer of 2012. This deal will have been tied up long ago, he hinted many times over the course of the season where he would be returning (before Ferguson retired) and poo-pooed links to Old Trafford in the MUTV interview with Crerand. I'm not saying that he wouldn't have been interested in the job, but some sections of the media and some United fans were absolutely convinced that his whole career was gearing up for the be all and end all of replacing Ferguson - without a scintilla of evidence to support it. He loves London, he owns a house here and his daughter is at college here. There are plenty of contributory factors other than "MUFC are MASSIVE - ergo he is desperate for the job".
It smacks of arrogance and assumptiveness to me.