[bumby]

I think people forget that the country was still somewhat raw from 9/11 and didn't know how to treat the uncertainty regarding future attacks. This was the timeframe when the "1% doctrine" was proposed, where if a threat was thought to have a 1% probability, it had to be treated as a certainty and response was more important than analysis.[1] In that context it doesn't take much to convince someone, even if in hindsight, Powell's presentation was "less than convincing."

[1] https://en.wikipedia.org/wiki/The_One_Percent_Doctrine