The ND defense was very good all season on 3rd down, and actually OSU was not good on 3rd. That flipped in the game. If the defense had caused either two punts or even gotten the fumble out on Egbuka when it almost happened on the second OSU drive, maybe the game is closer or even a win.
ND's second drive was killed by penalties, and the third drive of the half had the snap error on like 3rd and 5. By the next real drives they had it was 28-7. Failed the fake punt, now it's 31-7.
I'm not disagreeing with you that the offense had problems, but your argument that the defense somehow played lights out when OSU went 5/5 on their first 5 drives for 31 points, is not accurate. I am also not blaming Golden or saying it was because of an NFL gig. Sometimes the other team just beats you regardless of how well prepared you are. I do think injuries and possibly fatigue finally caught up to the defense when faced with an offense with the amount of weapons they had. The offense shot themselves in the foot two drives in a row. The difference for this team this year, was that when the offense faltered, the defense or special teams usually picked them up. That did not happen in this game.