That's why you're living in a fantasy.
The underestimation was not of what Saddam would do. The underestimation was of how far his troops/Fedayeen would go, even to the point of killing their own civilians and soldiers.
But this has been done in the past.
Even BEFORE the "war" started there were "reports" that they might be staging fake "attacks" on their civilians and blaming the US for it.
But we are SURPRISED when they have no problem killing their civilians.
Fascinating.
And it may not have been that much of an underestimation...there is a large contingent of special forces performing covert operations in Iraq right now.
Okay, we were surprised, but not really surprised. And, if you would read the other articles, that "large contingent of special forces" is the reason why the "war" is having the problems it is.
Rummy vetoed the generals' request for more troops. He wanted a high-tech, small-footprint army to go in.
So that "large contingent of special forces" is a symptom of the failure, not the success.