Have you read any of the many insider books about the Bush/Cheney administration's selling of the Iraq war? If you have, you will know that the NIE was written as a sales brochure. It was cooked. The many strong opposing opinions from the intelligence community (on key issues like the aluminum tubes and the yellow cake) were either omitted entirely, or buried in obtuse qualifying footnotes. Read Suskind's "The One Percent Solution" for a full explanation of the aluminum tube caper. The administration knowingly left out the real story from the NIE and all CIA documents.
Even though the books were cooked, as you say, there was still plenty of evidence that BushCo wasn't being straight up. Heck, even people as different as Gore and Webb thought Iraq was a mistake beforehand. I just don't think a lot of Senators gave a lot of thought to what going to war with Iraq(and the possible aftermath) meant. In voting for war, did they think Bush would handle the post-Saddam period well? Did these people not know The Decider's history? And the history of Iraq?
