The last time the Pats didn't make the AFCCG, the Steelers capitalized and went to the Super Bowl. From 2001-2010, their strategy was basically "hope someone else beats the Pats, because we sure as **** can't". But after 6 straight Patriots AFCCG appearances, it looks like the Steelers may be realizing that strategy no longer works. You simply can't make the Super Bowl in the AFC without beating the Pats.
I'm sure they'd rather not change their defensive identity in response to one team (a team that isn't even in their division, no less), but the Pats' utter dominance of the AFC this decade hasn't left them with much choice.