The US is a dying industrial economy. Despite protectionism of its farmers and heavy industry it knows it cannot win without focusing support on its services sector.

Here are just a few key beneficiaries of 9/11 and other 'terrorist' attacks.

Property developers- national accounting for economic growth abstracts from destruction and only counts construction. If you blow up a building you lose nothing but if you build one on top of it you have economic growth.

Arms companies
Not just profits from retaliatory wars but also developing the technology to increase surveillance of society under the guise of counter-terrorism. So you have BAEs "Onboard Threat Detection System." which consists of tiny cameras and microphones implanted in airline seats.

Private security companies- who can fight the wars and protect the homeland

the CIA - who can preserve and expand their bureaucracies. After all what exactly was left for them to do following the end of the Cold War

politicians- not only lobbied by the above but political campaigns always benefit from having a villain

Quite a formidable coalition