They're closer than I expected, but on the other hand, the Carolina-Arizona match-up was against two of the smaller market teams. I couldn't find the rating numbers, but in terms of viewers - Lions-Cowboys, 42 million, Bengals-Colts 28.3 (same as OSU-Bama), Ravens-Steelers 28.0, Panthers-Cards 21.7. Similar patterns in the prior years - top wild-card weekend game is in the 40s, avg viewers in the low 30s.
That is against OSU-Bama, which is about the best matchup you could plan for in college football. Would Mississippi St - Michigan St have fared nearly as well?