New England comparatively and certainly Vs Seattle didn't have a run 'D' in that situation.
If Seattle runs the ball with Marshawn Lynch it's abundantly probable that he scores a TD.
Belichick bet on the more probable of two "I need to be lucky situations" to make the defensive play:
Seattle showed pass and Bill Belichick set his defense (defensive backs) and hoped to defend pass and get a turn over.
At the end of that Super Bowl day:
Belichick arrived again as "Hoody Genius".