The field goal was the right move. It is still a two score game.
The FG was stupid. No way the Pats score at all if they get the ball inside their own 2. Worst case scenario the Steelers are still down by 14 but start at midfield. Instead they're desperate, throw the interception and it's over.
Going mincing in the playoffs always leads to defeat, there is no tomorrow always try to win. It's not college, there is no punishment for margin of loss.