well i feel their are a few common sense reasons beside the revenge factor and such.
It was unfinnished business. Saddam agreed to quite a few concessions after the 91 Gulf War: He didnt come across on half of them.
Our 10 year treaty for oil concessions has come to an end in Saudi Arabia; its time to find a more acessible oil market for the next 10 years for the folks back home.
Both sons were coming into their age for rule and possible rally of their folks to another war..time to get rid of them.
with the possible pull out of Turkey from its US treatys, another forward area needed to be found for that area. Remember, its a strategic commerce and travel choke point of the world.
With a possible shift in Saudi Politics, once again we were looking for a balance country in the locale...much like when we were in Iran with the shah to balance out the arab world on the other side of Israel.
My favorite belief...because it had to be done, and we could do it