1945 a plane hit the empire state building looked like this. Building 7 several blocks away collapsed by being hit with sharpnel alone is the commssions report not even an object. And to put it all into perspective this is what a 500 kg Warhead on a missle travelling mach 7 does to a building.

It's the kerosene that burnt in the WTCs, the high temperatures weakened the steel construction and made concrete brittle. Not much conspiracy here, just physics.