That's not a conspiracy theory, but a verifiable fact: the systems of control overtly implemented after 9/11 justified by terrorism had largely been proposed (overtly), by many of the same people pushing them after 9/11, with other justifications (often, in the most recent prior attempt, the War on Drugs was the justification.)
There is a related conspiracy theory, though, that 9/11 was engineered (either a false-flag op or simply knowingly allowed to proceed) for the purpose of being used in that way.
The real kicker? It aired in March 2001. That 9/11 conspiracy theory is older than the actual attacks!
These are overwhelmingly right-wing conspiracies.
> Similar sentiments exist for Big Agri/Food, particularly with GMOs.
These run across the board.
Back in the W Bush days there were suggestions being thrown around that homeland security types were using 9/11 as an excuse to push their pre-prepared systems of control on people, that Diebold voting machines were rigged to support Republicans.