Peter Beinart has some interesting reporting on why Chuck Hagel performed so poorly. Hagel was told to be as non-confrontational as possible and sent to pacify the lions with carrots:
All nominees are warned not to allow their hearings to turn combative, but a source close to Hagel suggests that the staffers prepping Hagel were particularly adamant on this score. "They expected [Jim] Inhofe, [John] McCain and especially [Ted] Cruz to come after him, and they said, 'Be a tank--don't rise and attack back.'" An aide involved in the Hagel preparations says that's overblown, but acknowledges that it was made clear that as a nominee, Hagel could not allow himself to be drawn into the kind of feisty exchange that Hillary Clinton had with Wisconsin Republican Ron Johnson during last month's hearings on Benghazi. This was considered particularly important in winning over those relatively moderate Senate Republicans like Tennessee's Lamar Alexander and Alaska's Lisa Murkowski, who administration aides believe like Hagel personally, and can be convinced to vote for him, or at least to oppose a Republican filibuster.