#1. Vince McMahon is a big fan of AJ Styles

Mick Foley once said that to be pushed by Vince McMahon, he needs to be a fan of yours. It's safe to say that Vince McMahon is, in fact, a big AJ Styles fan. His brief interactions with him at the end of last year towards the Royal Rumble further prove that, because McMahon doesn't randomly get involved in stories with superstars he doesn't have big plans for.
It was McMahon who lit a fire underneath Styles in 2016, telling him that he has plenty of guys who can do what he (Styles) does. What he wanted to see out of him was a Pitbull and a Pitbull was exactly what he got.
He has 100% faith in AJ Styles as a top superstar and if not now, there will be a time when Styles becomes Universal Champion. McMahon, being a big fan of his, may not want to wait to pull the trigger on The Phenomenal One.