"A measure of abnormal long put volume was also examined and seen to be at abnormally high levels in the days leading up to the attacks. Consequently, the paper concludes that there is evidence of unusual option market activity in the days leading up to September 11 that is consistent with investors trading on advance knowledge of the attacks".[67] —Allen M. Poteshman, The Journal of Business
The owner, Larry Silverstein, is literally on tape saying they told the guys to "pull" building 7.
"pull" is also a very common slang in demolitions for destroying a building.
It could be an op since he just blatantly said it on TV, but I really don't see how else building 7 could have fallen. Buildings don't fall like that after getting hit asymmetrically with debris.