Apparently, Congress agreed with the POTUS.
I think most of Congress thought the war would go well and they didn't want to find themselves on the wrong end of the vote come the next election. That's why so many have since run away with from their vote...blaming the President for the way he conducted the war...or trying to claim he ginned up the intelligence. I have respect for those who took a principled position...either for or against...I have nothing but contempt for those who play politics with decisions as serious as whether to send American troops into battle