Continuity mistake: When Kay visits Michael in hospital the oxygen tube is sometimes running under his shoulder, sometimes across the pillow. (01:07:55)
Visible crew/equipment: When Zasa's two henchmen try to kill Vincent and he shoots the second one through the hand, you see a bulge in the guy's palm just before it explodes to create a 'hole'. (00:34:30)
Continuity mistake: When Mary asks her father if she is just a front of the foundation she holds her arms to her chest. When the camera angle changes her arms are crossed on the table. Also her hair falls over her shoulder totally differently. (00:44:15)
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, making the Corleones respectable landowners. Michael owns 26% and is attempting to buy out the Vatican's 25% of the shares in it to gain controlling interest, 51% of the company. 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