You really don't know? Hagel is amongst those in DC who crave media adulation. The easiest way to get your face on TV is to be a Republican willing to voice disapproval of Bush (or any other Republican). Hagel has, in one way or another, told the media that ANY time they want a Pubbie on camera taking shots at Bush, he's their man.
If you take a look back at news stories mentioning Republicans taking a contrarian view of Dubya's policies, 99% of the time it's Hagel, followed by McMaxHeadcase of AZ. The networks have those two on SpeedDial.
Hagel just loves to be on TV and the media love to have him on. Simple.
Michael