re: Explain what caused the towers to collspse.

Massive amounts of weight must be distributed in a perfect structural form...otherwise it cascades into a domino effect with each domino exponentially increasing the force of it's momentum and mass.

Now if you are implying conspiracy 'actors' outside of bin Laden's purpose...I have no idea if such occurred. But given what we have witnessed from our supposed altruistic 'Leadership' in the last few years, I would not take anything off the conspiracy table. The Leadership deserves ZERO trust as they cya out the wazoo doing their 'national security' dance. The 'government' now has become THE national security threat, as it turns on the very (Constitutional) Freedoms which it purports to serve.

Herding cats coming.