Right ... Force = mass x acceleration ... things are required to accelerate as they fall ... the way we build our buildings, when a structural element falls, it fails catastrophically ... the video claims the under stories were "pulverized" which is completely non-structural ... the entire building would have fallen as a unit ... remember, once the one floor's vertical supports failed, the entire building's vertical structure is severely compromised, you can see the wall splay outwards as the top section falls down ... plus momentum, A LOT of momentum ... each individual connection within the building failed catastrophically and immediately ... that's just how we build things ...
By the way ... how did the lower part of the building get "pulverized"? ...