You know how they used to say if you threw a penny off the Empire State building it would go right through your head and out your ass? Maybe not but I
do, my point is imagine what a two ton steel column would do to you or a piece of concrete or marble bathroom flooring or a computer monitor or a desk
or whatever else was in that building that was not a five ton steel column. The falling top of this building turned into a friggn massive chainsaw
chewing, chopping, dicing, slicing, hacking, pounding, you get the picture right? Too many people wrongly think of this as two separate solid smooth
objects, one falling a couple stories on top of the other perfectly flat, level, plumb, evenly across the other with all the supports lining up
perfectly to resist the kinetic energy of the other, therefore the collapse needed additional explosives to remove more of the core columns so the
upper building would fall at free fall speed.
My theory of how it fell goes more along the lines of what is shown in this video with two exceptions. One- the outer skin peeled away more like a
banana skin in large sections and two- some of the core columns were still standing after the initial mass fell down and destroyed the structure
around them. Something to keep in mind is that if there are core columns still standing after the initial collapse: one-they were not cut in half with
explosives and two- nothing substantial hit them or crushed them. How is that possible if a 15 story solid mass landed on them? Wouldn't they be
crushed? But if the collapse happened more like the OP's video it would be possible.
I made this video for Anok to exemplify my point about the standing core columns
