The only way the material below is in motion is if it was already "failing", ie: blown up, cut or whatever. Otherwise the falling stuff above gets stopped or slowed by the still sturdy structure below.
My belief is that if the steel actually did soften and weaken ... and i think it is absurd... the structure would have maybe squashed a bit at that point... they'd have to renumber the elevator buttons, 77, 78, 79-81 crawlspaces, 82, 83, etc. Or because the steel weakened and had missing pieces at the side the planes hit while the other end was unaffected the top of the tower would tip off to that side and they'd have a 79 story WTC. It would still have been a nasty mess.
But nope, floors that people were walking around on just crumbled into dust for no reason. Blame them damn Muslims,eh?
