When Bush said he was going to attack Iraq as part of his War on Terrorism, this didn't seem very convincing. Sadam did not have a lot to do with Al Qaeda, except for some splinter group in the Philipines. No direct connections have been discovered since the overthrow of the regime.
Iraq has turned into a playground of terrorists on the other hand. 20 minor attacks a day and every week or so a really big one. It seems that this terrorism isn't home grown either: from all over the world Islamic hardliners move to Iraq to fight the Great Satan. So Bush gets to fight terrorism in Iraq after all.
This is probably not the original plan. But it is a way to catch terrorists. Invade a country and make it clear to Terrorism International Inc that this is the place to do business. Then, if you have them all within that country, catch them. It is like a big mouse trap. The bait is set. Now let's hope the mouse doesn't get way.