The decision -- its urgency -- seemed to come out of nowhere.
The thing that still baffles me today. It seems bush and co gave a few speeches and all of a sudden everybody was jumping on the bandwagon of war.
The best explanation I can think of is that lots of people wanted to a see a good old fashioned war/ass kicking (much like the europeans in the summer of 1914, who were very eager indeed to go to war), so they did not bother questioning the administration.