Milan can field some strong stacks but usually its an agressive faction and can expand rather quickly given the opportunity. I'd say you are seeing one of those random flukes that pops up every now and again. For Milan to not have expanded beyond two territories is more uncommon than common IMO. Considering it didnt expand I'm not suprised you are seeing alot of army stacks just standing about. When these flukes happen the offense expansion may not take place but the military build up continues. Its been know to happen with other factions as well. Just a game fluke.