near the 'Field Goal Choke Hold' zone, when it's better for the offense not to score a TD and better for the defense to allow a TD. But fortunately for GB, they had all 3 of their timeouts, and could be assured of getting the ball back with 1:27 to play if they made a stop and forced the FG. So with 3 timeouts remaining, the numbers say it never makes sense for a defense to intentionally allow the TD.
But GB jumped offside on the FG attempt, and gave PIT a 1st down and goal from the 5 with 1:35 to play. Now GB had only 1 timeout left, and it would have certainly made sense for PIT to refrain from scoring the TD, burn time off the clock, and kick an easy FG for the win.
The chart below illustrates when a defense would prefer to allow a TD. The black diamond represents the state of the game at the 1st and goal mark assuming PIT does not score a TD. The black line shows the win probability of the defense if they allow the TD.
In normal conditions, playing for the stop and a FG yields only about a 1% chance of winning for the defense, which essentially is the chance of going to overtime based on a botched FG. But getting the ball back with 1:30 to play down by 7 equates to about a 9% chance of winning. That assumes a 50% chance in OT and about an 18% chance of a successful TD drive to get there.
It was an excellent opportunity for GB to use the intentional TD tactic. PIT was apparently determined to get the TD and either completely unaware of the FG choke hold concept or, as I'll discuss below, too fearful of the FG attempt. On previous plays PIT was throwing into the end zone rather than throwing for just the 1st down or running the ball. If they had been aware, they would have preferred to throw underneath. And on subsequent downs, not only did they appear desperate to get into the end zone, grinding for every inch, they ultimately betrayed their intention by actually scoring.
It was mentioned that PIT head coach Mike Tomlin may have been dwelling on GB's blocked FG attempt on their prior possession. It was a block on a very short attempt, also from the 5 yard line. This is an extremely rare event, occurring far less than 1% of the time. But the conditions were snowy, so he may have thought the chance of an unsuccessful FG attempt, due to a block, bad snap, bobbled hold, or anything else was higher than usual. That's a good consideration, but the chance of an unsuccessful attempt would have be several (~9) times higher than typical for it to make the difference.
Sure enough, within seconds GB had a first and goal threatening to tie the game. They were unsuccessful, partly due to self-inflicted errors of their own, but the principle stands. PIT should have run out the clock and kicked a FG. And GB should have intentionally allowed the TD.
This is what I call the NFL's sub-optimum equilibrium. Neither team does the smart thing, so no one pays the price and (almost) no one notices.