Why did he start the war?

Anyone know why president George W. Bush had the Iraqi war started?

We might think of several reasons, but none of them seem to be relevant or adequate to justify the war.

How about this one:
- Well, he tried to kill my dad, didn't he?
- So I killed him, didn't I?
- That should teach him a lesson!

But the war is still on even though Saddam Hussein is long gone. So that cannot be the reason. Not the only one anyway.

Does anyone know, why...