somebody did the math to determine how much energy would be needed to turn that much steel and concrete and furnishings into dust before it could hit the ground. they concluded the buildings would need to be constructed mostly from explosives in order to achieve this. not to mention the dust cloud from this effect would be pyroclastic (but it clearly wasn't on that day as nobody was burned by it). what we witnessed (and the world at large witnessed) that day was a demonstration of exotic weapons technology. I like to call it the Jewish Space Laser. Many people think that is antisemitic, regardless of its truthfulness.