Well, it helps when the Pats have their best two recievers and tight end down. As much as I respect Brady as a QB he isn't superman and there is only so much that he can do with backups to backups. I think that, all things being equal, the Bears would have been competitive today against Denver.
Denver got New England at the right time. The Pats were hurt, Brady hasn't had the comfort level he usually has and Osweiler did exactly what he needed to do to win the game. It also helps when your team puts up 179 yards on the ground. I'm not faulting Osweiler for his performance, it was good enough but lets not start talking about how great he is after he puts up a 72.1 QB rating against a team with similar overall defensive stats. If anything he should have put up better numbers against the 19th rated passing yardage team that is the New England Patriots.
He could be good, he could be crappy. Remember Sanchez looked good for a short time too.