The likely knew what they were going to run in the first half as well. It isn't like this offense has a ton of plays.
In the first half, the steelers could have success because they didn't invent ways to screw themselves. In the second half, they conjured up multiple ways to face 3rd and forever.
On a sidenote, I think Pratt is a FA this off-season. Bengals may not be able to pay. Anyone come away from most Steelers-Bengals games somewhat impressed with his play? Maybe it is just me...