For bureaucratic reasons

Billmon has a long list of Bush regime quotes about weapons of mass destruction which follows a blazing arc from this:

Intelligence gathered by this and other governments leaves no doubt that the Iraq regime continues to possess and conceal some of the most lethal weapons ever devised.

George Bush
March 17, 2003

to this:

For bureaucratic reasons, we settled on one issue, weapons of mass destruction (as justification for invading Iraq) because it was the one reason everyone could agree on.

Paul Wolfowitz
May 28, 2003