Other mistake: The close up of the Wall Street Journal mentioning Immobiliare seems to have operating instructions for a Windows program under the headline. The newspapers previous to this appearance also have a headline pasted onto another news topic altogether. The same happens later with the newspapers covering cleansing actions of the new pope. These papers date from March 27, 1980, although the events are supposed to take place in 1979. (00:41:42 - 02:00:00)
Other mistake: Before Joey Zasa is murdered, an altar boy in the parade (on the left side of the screen) can't help but stare at the camera all the time.
Answer: Michael is trying to divest the family of all ties to organized crime. Internazionale Immobiliare is an international real estate concern and owning it would legitimize the family. Michael is attempting to buy out the Vatican's 25% of the shares in it to gain controlling interest, but the other families either want in on the deal or want to steal it out from under him, forcing him back into his old criminal ways.
Captain Defenestrator