re: Explain what caused the towers to collspse.

You don't need an engineering degree to listen to structural engineers, physicists, and hundreds of other scientists state that buildings don't fall like they did without help of explosives in the right place. When is the last time you saw a plane or any moving object hit something and not slow down? Physically impossible. Videos of the first plane going through the building and coming out the other side with the nose cone intact which can't even take a bird strike without damage.
Building 7 fell why? Just because you saw something on TV doesn't make it true unless you also believe Godzilla is real too. Money and Power will make a lot of people do terrible things and this was one of them.