Uneven support, caused by the weakening of the structure on the side were the plane hit. There is nothing inherently dubious about that. The problem is the lack of the rotation of the block being reflected in the destruction bellow it.
However, that video does show an curious cloud of dust and debris rising from the upper section of the building after it tumbles off to the side, but before it has a chance to hit the ground.
It also shows a curious burst of fire off to the right hand side at 4 seconds in, but I suppose that was just oxygen being pushed into an already burning fire by the collapse?
And if the weight of the building itself was crushing everything below it, rather than an artificial weakening of certain parts contributing to it, why was there still a big spike of the tower left upright momentarily?
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