Award or not, AJ was the definition of a steady hand at the wheel the entire regular season.
And he managed the hell out of the postseason.
I only watched Hinch manage with regularity after the all star game and I think he should get credit for successfully handling a lot of injuries among other things. And I haven't watched Molitor manage a single game, so I can't speak to the justness of the decision.
Most (all?) of Hinch's starting rotation had injuries real or imagined at some point of the season. Also had stretches where key position players were hurt too. Even had to deal with his emergency back up pitchers having problems of their own (Paulino). So sure, maybe Molitor got a lot out of a team with considerably less talent, but it wasn't smooth sailing on the road winning the division (a hurricane comes to mind).
Things like manger of the year are pretty subjective, expect this is award may be like an Oscar, where you sometimes win in a specific year in order to recognize your career, not just a specific year. No doubt people are paying attention to him now and wouldn't be surprised if he wins one in the next year or two.