Didn't play up to expectations is the answer.
Over the last decade the Buckeyes lost a series to USC, split with Texas, split with Miami, laid a turd in two recent NCGs. This season they had to outscore a one-win Cal team that carried the game into the 4th quarter, gave up half a thousand yards to Abracadabra, struggled with Northwestern, gave up 35 points to an Illini team that spit the bit seven games ago, played in a conference whose second best team lost to Notre Dame and whose third best team lost to Arizona State, and whose other teams lost games to two MAC teams and Cincinnati. Throw in the that of the other two B1G teams with any name recognition, one is being punished (justly) and can't go bowling and won't be "back" anytime soon, and the other is living up to it's name as a "public Ivy," this time by playing Ivy level football.
Some of it is perception, but some of it is self inflicted. How can you be short of talent at line-backer for 3 straight years (and remember, no one outside of Ohio knows what happened to recruits that didn't pan out)? They just look at this D and wonder what happened at a school that always seemed to have plenty). Some of it has to do with the fact that Michigan is a joke that gets exposed week in and week out. Some of it has to do with the fact that no one outside the B1G - and plenty people within the B1G - gives a [Mark May] that all the BCS bowls are in the sunbelt, that all B1G bowl teams are playing away, or that B1G teams tend to have to play up in the bowls.