Something happened to Powell prior to his dramatic UN presentation, the one many ET members derided him for (you know who you are).
It was being portrayed as a Powell v.s. Rumsfeld & Cheney thing, Powell the peace-loving diplomat v.s. the hawks. Something happened to convince Powell that Rumsfeld, Cheney, and the big boss were in fact correct.
Prior to his conversion I was wondering why he was so patient with taking the dovish side, considering his role in Desert Storm. Maybe he really believed a diplomatic solution through the UN was a viable route, or maybe he was thinking of his future political career. When all is said and done, his role in all this will be remembered for taking the slow & careful route. Whether or not that will backfire on him down the road remains to be seen.
In any case, he's a sharp guy and we're lucky to have him.