I think this outcome was a combination of two interdependent factors:
1) The coaches called the game aggressively because they trusted that Allen could turn it on at any minute.
2) Allen played a subpar game.
The coaching staff refused to make the necessary adjustments in light of Allen’s play. They kept calling an aggressive game and putting it on Allen’s shoulders when the correct thing to do was start playing more conservatively after the 1st half.
That, in turn, did not help Allen. Some I formation sets with runs and play action was the correct adjustment. Instead, they kept going 5 wide and running QB draws, playing into the Steelers’ strengths.
Overall, I think coaching adjustments are easier to implement as opposed to not adjusting to how your QB is playing and expecting him to ball out.