I agree. Tenet told him that Saddam was close to going nuclear, so he invaded. When a thorough search disproved the intelligence, he switched to democratizing Iraq. This has improved impossible because there is no Iraqi nation-state. Now his creativity and room for political manuever is at an end. His successors will have to clean up his mess.
There were valid reasons for going into Iraq, IMO. I always thought the main one was just to create another victory against a radical Islamic state, and thus another victory in the WOT, another demonstration of why you don't mess with America. A demonstration that would go a long ways toward discouraging other terror groups from perpetrating another 9/11 or worse. Much worse is the fear, I believe. Saddam was a clear danger to the civilized world, so taking him out was something of an obvious step. I'm sure Bush hoped for an entirely new face on the Middle East once this was accomplished.
Unfortunately, for whatever reasons, probably politically correct reasons, irregular radical Islamics, some allied with Al Qaeda, have been able to resist our forces, and we are now on the verge of retreat. I hope W can pull a rabbit out of his hat now, because if he can't, this adventrue will have, instead of cowing terrorists, given them a great victory. Instead of being safer from them, we'll be in greater danger. Instead of a more pacified Middle East, we'll have a nuclear one, possibly dominated by our enemies, the Iranian mullahs. We'll be looking forward to WMD's being set off in our cities, with all the ramifications that come with that, wrecked economy, possible martial law, end of our way of life, etc.
W's the president, so he'll have to bear most of the blame, or get most of the credit, for whatever consequences ensue.