There have been a lot of great players on average teams that put up good or even great stats and ultimately take their teams nowhere. There's a difference between a team standing back and letting a great one-on-one player go to work, versus a team that designs an entire system around a player especially when that players individual stats may even drop to make the team better. And there's a reason why players on perennial championship contenders are considered all-time greats when their stats may not be as good as some other dude who's the only guy putting up numbers on a shitty team.
Not that the MVP even matters. Only good players on shitty teams really care about the MVP as they know that's their championship. Which is why I wouldn't be surprised if Harden won the MVP and struggled in another first round playoff loss.