Hamilton has just been playing a good guy on television, while behind the scenes, he's given free rein to uber liberal lawyer, Ben Viniste. And Kerrey "went Hollywood" long ago, even before Actor's Studio and New School.
I think you got Kerrey pegged just right. "Not serious", even worse, a soundbiting showboater, and disrespectful of his duties. I'm thinking he took the job only because he knew the staff would do all the work.
Why did Hamilton and Kerrey rudely leave early? Most likely they were totally ticked that Bush was doing so well with the committee. And they were snoockered from the get-go. With Cheney there as witness, the committee wouldn't be able to leak lies without the White House's immediate response.