It's not like this is something new from Tomlin. You may recall the 49ers game back in 2011, when Ben was wearing a walking boot the whole week prior to the game for a bad ankle. He was getting pummeled by an aggressive San Francisco defense all night. The Steelers have been completely dominated, and are losing 20-3 with 2 minutes left in the game. MT actually sends Ben hobbling out there to start a drive from their own TWELVE yard line with no timeouts left, drops him back to pass three times, and punts it away after Ben got hammered yet again on third down and fumbled.
There's just no explanation for that level of stupidity and/or stubborness from an NFL head coach.