Why can't the experts demonstrate the force behind the motion?
This is not an attempt in any way to build a scaled model of the towers. Rather, dissimilar objects can be used to study the motion of large objects as the direction and sequence of net force are both independent of scale.
For example, the motion of a bucket on a rope whirled around your head is similar to the motion of the moon orbiting earth. The direction (not the magnitude) of net force acting on the bucket and the moon is similar, even though the bucket is not a scaled model of the moon.
Any objects observed to accelerate similarly, will have the same direction and sequence of net force, regardless of scale.
No one has been able to make a real model demonstrating the fundamental motions observed of the towers fall, using gravity alone.