I think he realized he isn't as good as he thought he was. Not hating on Jake at all, but his team are "yes men" and, combined with his success against low level opponents, he started to believe his own hype. He managed to scrape a decision against on old, shot, 4-fight losing streak, not-even-a-boxer Woodley but couldn't even finish him, and now he's starting to see that he doesn't have that much knockout power. Best to retire now because honestly this is his ceiling in boxing. Any step up in competition here would go poorly for him (Masvidal, any real pro boxer, Anderson) and fighting other amateurs and Youtubers wouldn't draw interest now that he has W's against two UFC fighters.