One theoretical conspiracy involves personnel carrying around large explosive charges and drilling holes in strategically placed beams on every floor of a permanently occupied and secure office building unnoticed by any one of thousands of surviving workers. The other involves a truck in an area the US is known to be conducting military operations unloading stuff at an abandoned remote facility and then calling in non-conspirators to validate their 'find', and accusing any Iraqi who argues the facility had other purposes of lying. Not saying there aren't reasons the second wouldn't go wrong - from getting ambushed or inspected en route to UN weapons inspectors concluding the material is unlikely to be of Iraqi origin - but it's not more difficult to plant stuff in a remote location than secretly prepare for a controlled demolition of a heavily occupied skyscraper.