Coaches probably have lots of reasons. I think that there is something to winning a game, even if it's just preseason. It gets morale up. Losses also can act as a wake-up call. Maybe he thought that team chemistry needed the win, so they actually played for it. Who knows?
Actually I think he was playing for the win. If he had gone for a PAT, NE would have needed a FG to win. By going for 2, it meant NE need a FG to tie and a TD to win. He knew there is no way BB would kick a FG to create a tie, thus forcing NE to go for the first down/TD, if NE was on fourth down and in FG range.