The Seahawks used a very unique (for them) gameplan versus the Rams, a departure from the style that they normally play in the last few seasons. It almost worked. Despite only completing one pass downfield of over 10 air yards, Russell Wilson finished 32 of 41 in passing, many of these short passes left the Seahawks in 3rd and very short.
The Seahawks found themselves in 3rd and 1 five separate times (I can't recall a game in recent memory with so many of this distance) and they converted all of them successfully via running back run. They also converted a 3rd and 2 via the run.