The point of allowing expectations to remain unrealistically high was to encourage waverers in Hussein's entourage to turn against the regime very early and end the war even before it began. It was a good idea. It did not pan out. But given the possible benefits, it was certainly worth a try.
The regime did not collapse overnight. Hence Plan B, an adapted version of the original war plan. It involves real fighting and real losses. Plan A, in contrast, while always plausible, was a hope for the miraculous. It was a kind of anti-war plan, as it would not have required any real battles at all.
The miracle having not happened, we are now fighting a conventional war. And winning -- thanks to the Franks plan and its flexibility, and despite the carping of those who, in conflict after conflict, see Vietnam in anything short of immediate immaculate victory.
Análise lúcida de Charles Krauthammer no Washington Post, sobre as espectativas de uma guerra rápida: