Capturing state power, or sabotaging a state that they cannot control, is the dream of all statists around the world. Change, for better or for worse, can only be done via the state, nothing else.
Most radical statists would target government structures, military and police agencies in particular, and kill as many government officials, soldiers and policemen as possible, not civilians. But OBL and his warriors, and several other terrorist groups around the world, would prefer to kill civilians -- you and me, our family and friends, non-combatants -- to achieve their short- and long-term goals.
The BIG government of the US, is the main enemy of many terrorists, communists, and other statists on the other side of the fence. BIG states, whether democratic or totalitarian, always result in more coercion and subjugation of the individual. They only differ in the extent or level of coercion.
It is important that people express their views as openly as possible. This reduces the need to go for violent means of criticizing or attacking BIG governments. Killing civilians, blowing up big civilian structures, are wrong and criminal. We civilians can give credit to a BIG and armed government, like the US government, if it does its important job of protecting the citizens' right to liberty, right to private property, right to live peacefully.
It's another thing though, when that same BIG government will invade other countries for oil or other business and political interests. Or support many dictatorial governments abroad that kill many of its citizens, provided that such dictators will remain friendly to it.
And this is how OBL' statism exhibited another failure. They criticized only the US government's foreign policy and "imperialism", but they are silent of the monarchies and absolute dictatorships that rule the Middle East, Africa and other regions.