I think it's less "under Ole" and more "not under Mou".
I'm not at all surprised. The players had every incentive to perform now that Mourinho is gone as it would shift any blame for our previous poor form entirely onto the manager. That's true for Pogba more than anyone else given his relationship with Mourinho.
A very talented player with a point to prove, an easy run of fixtures and a manager who knows him.