Edit: Because the former doesn't sound like much of a conspiracy, aside from a cover-up afterwards.
Just like assassination of Austro-Hungarian heir Archduke Franz Ferdinand brought domino effect and caused First World war the same would happen now.
expanded abilities of law enforcement to surveil, including by tapping domestic and international phones;
eased interagency communication to allow federal agencies to more effectively use all available resources in counterterrorism efforts; and
increased penalties for terrorism crimes and an expanded list of activities which would qualify someone to be charged with terrorism.[1]