" So explain the other tower that collapsed. The third tower"

You mean the one that had several thousand gallons of petrol stored on floor 10 or whatever, to run the 'Crisis Center"... :-)


If you burn enough flammable fuel for long enough, things get so hot that 'steel' loses its temper, thus loses its designed load bearing capability...

Fall down - go boom!

Trust me, I'm a trained blacksmith... :-)