Link from OSU blog

[HawkeyeDenis]

I thought the turning point of the game was the penalty on Bosa. It was tied at 17 we had the ball at about midfield on a 3rd and long. If he didn't headbut Stanley we are punting it back to them. (maybe?? Probably) but instead we get 15 yards and next play Stanley drops the ball in the bucket to Fant and that gut punch started the 31-0 run. For whatever reasons Urban totally bailed on the running game. Dobbins should look to transfer after that game for the lack of using of him. I guess Meyer thought Barrett could do what he did against PSU and just play like superman but for crying out loud no QB can pull off what he did there twice in a row. Especially on the road against a team that their D couldn't slow down.

Having watched the game 4 times, I would say that the expulsion of Bosa added to the momentum that Iowa had. Iowa was setting the pace in the game, Iowa would score then Ohio State would answer. Iowa basically was dictating the pace of the game. Ohio State went away from their running game to a pass heavy game.
In the second quarter, Ohio State's loses two offensive linemen, albeit only for a few plays. It's 17-17 when Bosa gets ejected. Iowa scores right after that. It's 24-17. Before the half, Barrett throws another INT. Iowa scores again. It's 31-17 at the half. Ohio State was totally out of their game plan and not able to adjust. They came in expecting a certain game from Iowa and Iowa showed them something totally different.