He was a useful idiot. By uttering “It’s a slam dunk”, and being a Clintoon appointee, he gives Bush/Cheney a CIA get out of jail free card in the upcoming impeachment trials. By cooking the intel, Tenet is responsible for misleading the Congress and the nation, not Bush/Cheney.
He didn’t “cook” the intel—It was consistent with the intel reports from around the world. But his complaint is stupid. And he was a rotten director of a corrupt, failing agency.