What came out later is that State Department intelligence (yes, they're part of the IC) cast doubt on that information, and that Powell had even gone back to Tenant more than once to be reassured it was reliable. Powell's error was believing George Tenet over his own people. He should have said, "when your people can convince my people, I'll go with it."
I've met Tenet--shook his and and then counted my fingers. He is the type to go with the political flow anyway, but it's also known that Cheney made several trips out to Langley to make sure the CIA's assessment was what he and Rumsfeld wanted. Vice-presidential visits is a heck of a lot of political pressure on an intelligence agency.
Meanwhile, back at the Pentagon, the DIA analysts weren't giving Rumsfeld the ammunition he wanted and were leaking an opposing argument, so Rumsfeld created an entirely separate mini-agency of non-professional analysts "...to find what the others have missed" and give him what he wanted.
What caused me so much anguish at the time is how the media and the public totally missed how much the military was dragging its feet against the Iraq invasion, even to the point of senior officers openly disputing Rumsfeld, the Army Chief of Staff even got abruptly fired because he refused to endorse Rumsfeld's claim that the war could be completely won on the cheap with only 70,000 troops. The Marine Commandant held the same position against a cheap invasion and retired instead.
All the remaining "class of Vietnam" general officers actually retired before the invasion began.