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: It shows you how greedy they are even as they've made it to the zenith of their criminal careers. That's why you see Michael pass it on disgustedly and stare blankly into the ether. Michael's goal was never to be the boss or capo di tutti capi, he only did it to protect his father and then his family, his main goal. And at that moment he realises he's never getting out. He's a business man in a world of criminals (which he is himself).