Ask HN: Why hasn't anyone modeled the collapse of the twin towers

It seems the most controversial issue with the 9/11 attacks was that TWO towers collapsed in highly unlikely ways that physically seem impossible.

Even at free fall speed, there is nothing the top floors could do to generate enough extra gravity to collapse the floors below, like pushing on your own shoulders enough to bend your knees, it makes no sense.

NIST models assume zero resistance and top floors in free fall, it makes no sense but it's all they gave us.