It is a larger than average bet for sure, especially for NFL; it's one of the largest NFL wagers I've made this season.
I think Pittsburgh is molding into playoff form and playing at a very high level right now. I expect their offense to always give teams problems, but their defense is really playing well right now. I sincerely believe the Steelers are the second-best team in the AFC, behind New England and just in front of Kansas City.
Couple that with the fact that this is a Thursday night game at Heinz Field against a team that, while it's playing well, is prone to be inconsistent (especially Cam). I think the Carolina defense is the single-most overrated unit in the NFL; and I think the Steelers will exploit it and win with some level of comfort of tonight.
You never know in the NFL, but Steelers covering seems like the move here.