Activision fired them over nothing and blocked them from talking to others.
Activision Seeking Internal Documents Related To West, Zampella And...Electronic Arts?
Activision Responds To West, Zampella's Lawsuit, Company "Disappointed"
Kotaku.com -
To sum it up Infinity Ward didnt want to continue the Call of Duty franchise with MW3 before starting a new IP. In-turn Activision fired two key staff (Jason West and Vince Zampella) and put a new developer on the franchise.
He didn't have a son and we don't know how this universe X is made but if Jacob didnt touch them, people lives could be total different without Jacob or the island.