re: How'd he get so dumb between then and now?
As Cheney said the US had only 146 US military killed and they reached the agreed upon objectives of the war.
Why do something that could diminish that that kind of victory?
What Cheney didn't mention was we got a cease fire agreement from Saddam. Had Saddam not chosen to do this, the US would have continue the war [until they got such agreement or Saddam was no longer in power].
It was Saddam's failure to abide by the terms of the cease fire agreement, which eventually lead him to his spider hole and his execution.