Slate (in addition to various other media outlets) has been running a series of editorials by former Iraq war boosters on why they got the war so horribly wrong, five years later. In other words, why did they think that everything would be rainbows and kittens six months after the invasion?
This is a silly question. It allows these people to look back on their views and pontificate endlessly about how they were fooled, leading to an endless array of excuses. "Oh, the administration was so convincing" (seriously?) or "oh, September 11th made me so angry and afraid" (the one in 2001 that was in no way connected to Iraq?) or "oh, Saddam was a bad, bad man" (your point?).
I have yet to see anyone give what is the correct answer: "Somehow, I believed (despite all the historical evidence) that forcing our way into a country and completely upsetting their political system (not to mention killing a lot of people) would lead to the 52nd State of America. Yes, I am an idiot." Because that's really what it all boils down to, in the end. You can point to a number of intellectual distractions, but the fundamental problem is that pro-war sloganeers believe (note the present tense) that war is a perfectly good initial solution to their international problems.
Sadly, the fact that this is a really obvious error will not stop these people from being paid to offer their opinions for the rest of their natural lives. You get the pundit class you deserve, I guess.
Nobody seems to be particularly interested in paying people who were right about the invasion to expand on their views, perhaps because Daniel Davies already did it about as well as anyone could, for free.