So far, many common things seen everyday foreshadowed 9/11's events, such as the Simpsons, a Spiderman comic, and Johnny Bravo. All this, being hand drawn by professionals for large companies and not a civilian mistake, shows that some people might have been in on it.
There is a social effect where gradually introducing something into society until the final thing is released makes it seem not as bad and society is generally more accepting. This ideology is commonly used for movie trailers and phone or tech models. However this could have been applied to the 9/11 attacks by governmental orders so people would not be as shocked and would not be asking several questions about the event.
The government has done shady things with other nations, like Trump did with Ukraine for the reelection, so who can say they wouldn't do it for the 9/11 attacks?
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