Sadly, that didn't last long. They were obsessed with Iraq, so we soon shifted from pave the streets of Afghanistan with gold to SaddamoMuslims are going to KILL US ALL FROM BAGHDAD. The media happily followed the soccer ball as the Bushies kicked it from Kabul to Baghdad, and the real forgotten war and reconstruction - in Afghanistan - quickly faded from memory. Truly, we didn't think much about it anymore.
For all that anger, though, I recall that I also took it for granted that "we" -- the country, the government, the military, the CIA -- at a minimum were going to manage to get the bastards who did that. It hasn't, of course, worked out like that. We got some folks, but the ringleaders got away. We toppled the Taliban, but didn't really finish them off. And I remember self-righteously assuring the far-left types on campus who opposed the Afghan War that of course the USA would be fully committed to reconstructing Afghanistan -- it was a case where our moral obligations aligned almost perfectly with our narrowest interests in safety.
We truly had an opportunity to Do The Right Thing - the Grand Military Humanitarian Intervention that the Peter Beinarts of the world dream about - and we didn't in large part because the "liberal hawks" thought it was more important to head to Baghdad than to do it right in Afghanistan.
I don't entirely understand how this was possible. I suppose they, like Yglesias, were so convinced that of course we would do the right thing as anything else defied comprehension, even as unfolding evidence to the contrary was everywhere.
There's no way to answer the question of whether the Afghanistan war was the right thing to do - it was inevitable and there's no way to tease out a credible "what if" alternative history timeline - but it's reasonable to ask if it's been a net good. I have no ability to answer that question, but it's not something which should be taken on faith. We certainly didn't achieve what we should have, and those "far-left types" who worried that we were going to kill a bunch of people then screw the pooch certainly had a point.