Ranxxer I found you a crediable site explaining why the Towers might have collapsed!
http://www.civil.usyd.edu.au/latest/wtc.php
If it was a controlled demolition would 'It is evident that the building is falling over to the left. The North Tower collapsed directly downwards, on top of itself. '
I don't know anything about controlled demolitions and don't believe that is what happened on 9/11 but would a controlled demolition cause of of the towers to tip to one side before caving in?