Mou was originally the anti Manchester United per excellence. Sure he had that confidence, charisma and brilliance that a young SAF had. However his lack of patience with players (especially youths) and his over ambition that sometimes made him look a bit of a mercenary had not made him a very popular choice at OT.
I believe that his recent spat with Chelsea changed him. For the first time in maybe his entire career, Mou was ready to stay at a club and makes the necessary painful changes rather then just hop away from them as he did at clubs like Inter. It didn't turned out right for him. The owner didn't back him, information leaked to the team and right from the start Mou was a dead man walking as he lead a bunch of mercenaries who knew that the manager wanted them gone. I rarely say that but I can't think of any manager who would be in that situation and still be able to turn things around.
I believe that the timing is right as United and Mou need one another. We need a manager whose not only brilliant (LVG was a good manager too) but who also understand the club and the EPL. Mou on the other hand need a proper club that gives him support, stability and the respect a top manager demand and yearn for.
No one will ever be able to equal SAF's record. However I can see Mourinho becoming the second best manager this club had ever had. Maybe that's wishful thinking. However I do believe its a realistic goal