It's a fair question. Somehow I don't think that Novak sold Scooter down the river just to protect a source. Washington politics is incredibly tangled: there's probably a lot more to the situation than any of us ever knew, and Novak has carried it with him to the grave.
My recollection may have some fuzzy edges, as it has been a while since I thought about it but my memory is that Scooter Libby was sent to prison for a supposed lie. I am not sure that it was a lie, but that was the charge.
It is my recollection that at that point the matter of who “revealed” that Plame was CIA was moot.
The real villains in this sorry story are Armitage and Powell for not speaking up. They could have done so without jeopardizing anyone.
Although I would not go so far as to call Bush a villain in this matter, I do think that this was far from Bush's finest hour. He could have and should have granted Libby a complete pardon. In fact, he should have pardoned him before the trial ever took place.
Libby got himself into his own hot water. Novak owed him nothing. For all we know, Novak may have been interested in finding out just how much character the other players would demonstrate.
He did take an oath. There are people who consider their word their bond. The world would be a better place if we had more of them.
In my view, Novak was the only person involved in the event that had any character.
The prosecutor was a rat for even questioning Libby when he already knew Plame was no covert operative. He set out to trap Libby for some political reason.
Armitage knew what was happening and said nothing.
Powell knew and said nothing.
Bush knew it was a political witch hunt and did nothing.
And every single Bush operative should have walked out the door the day Libby was convicted.
I would have.