Allegris Milan just had the most firepower in the league when they won Scudetto - Ibra, Pato, Ronaldinho, Robinho, Cassano (iirc he joined mid season though). Rest of the team was ok, similar to Inter, Napoli and Roma, but that frontline was too much for Serie A.
Inter selfdestructed by hiring the clown Benitez and with that frontline Milan didnt really have any other opponents