Let me make it really simple.
It's the fault of all the pepole who wish to gather power by forcing everyone to do what they say. If there were no dictators, tyrants, or terrorists, we wouldn't have to fight them.
If Saddam Hussain hadn't been a brutal dictator who staughtered his own people, invaded other countries, and assisted terrorists with supplies of arms and training camps no one would have given a care what weapons he was collecting.