He didn't "left his job", he was kicked in the ass and fired by Sega because he used the company money with no permission to go to dinner (and after-dinner) with other other companies' big shots without telling anyone what the hell he was doing.
He got all the way to the top of Sega's gaming division (he's the reason Sega only made Yakuzas for years) and thought he could get away with anything. And now he has nothing