He saw OB's horrible challenge earlier and was not going to be out done. OB is on the goal line several times and doesn't call a running play for an RB, instead goes into shotgun formation several times and fails repeatedly. This infuriated Garrett, he was not going to have some in-state rival prove that he was the worse coach. Garrett bides his time, waiting for the biggest moment in the game to make the most questionable call of the game, which was full of questionable calls. He had to have a call so horrendous that it would totally nullify every other bad call from either bench, to the point people wouldn't even remember how bad those other calls were. It just goes to prove that Garrett will not allow himself to outcoach anyone, regardless of how much they fail.