I was coming here to ask the same. Dumb or aware of the line (12.5 in the league I'm in, not sure what the close was) are the only two explanations I can come up with.
I saw Petersen do something similar 6 or 7 years ago. It was a back and forth game with a lot of scoring. Boise scored a TD to go up by 8 late in the 4th. He goes for 2, gets it, and covers...but risked leaving it as a one possession game with only a few minutes left in the game.