I think it's that . . .
19 kamikazee muslims hijacked 4 commercial airliners and flew 1 each into WTC1, WTC2, the Pentagon and Shanksville, causing massive damage to the perimeter and core columns of the twin towers, stripping off the fireproofing and igniting raging fires and sending an unignited stream of jet fuel down an elevator shaft all the way to the basement, where it jumped to another elevator shaft, reversed direction and came up to the lobby, ignited and blew out the windows, then the aforementioned raging fires heated up the floor trusses to the point where they sagged and pulled inwards on the heated core and perimeter columns, eventually breaking them which caused the mass of the tower above to come crashing down on the floor below, pulverizing almost all of the non-metallic material into fine powder and shredding all 287 steel columns into roughly 30 foot lengths and ejecting said powder and shredded steel hundreds of feet laterally in all directions, then continuing downwards and doing the same thing to the next floor, and the next (while appearing to jump in 4 or 5 floor increments), occasionaly advancing a floor assembly 20 stories ahead of the collapse wave in a "piston fashion" which simulatneouly crushed drywall into dust, focused this dust into a tight jet pattern and expelled it out exactly one window on each of two faces of the building, continuing to add mass and speed above the collapse front while this accumulating mass became invisible and showed no sign of itself, repeating the "jet plume" trick several more times, proceeding all the way to the ground, where the invisible accumulated pulverizing slegehammer of destruction finally disappeared altogether and left behing a chimney of smoke with a distinct mushroom top, and billowing clouds of dust which looked remarkably like the pyroclastic flows of a volcano (but which weren't), leaving behind a very small pile of rubble, (considering the size of the towers) which somehow imitated a blast furnace inside and melted steel down for months afterward, meanwhile another jet crashed into the Pentagon leaving almost no sign of itself and no sign of its passengers yet somehow left DNA samples, and some round part of the aircraft travelled all the way through the building and stayed perfectly intact enough to punch a very round exit hole through reinforced concrete but then disappeared, meanwhile the forth jet crashed because brave passengers tried to wrestle control away from the hijackers and crashed the plane straight down into a field where it disintegrated and left no sign of itself whatsoever.
Gravy, I think that's what you're working with.