Short answer to "What happened to the WTC?"

In brief, the WTC was turned into dust that was foam-like in appearance and behavior. The dust cloud was a colloidal suspension of particles in air that acted as a fluid as it cascaded down the sides of the buildings and onto the streets of lower Manhattan. The majority of the mass of WTC 1, WTC 2, WTC 3, and WTC 7 was turned into dust, and much of WTC 4, 5 and 6 met the same fate (Fig. 1C). There were some oddly damaged steel beams left over after the buildings went away, but not much compared to the original mass of the buildings. The thousands of sinks and toilets that were located in the WTC were nowhere to be found in the debris. The concrete was gone. The glass was gone. Most of the steel was gone. It had become dust and rolled down the streets of lower Manhattan (Fig. 1B) and rose up into the atmosphere (Fig. 1C, 2A), except the paper. The paper survived (Fig. 2B), which meant that the dust itself was not extremely hot and therefore not the result of explosive devices or any other process that would produce ambient heat that was sufficient to ignite paper.

Two of the largest buildings on Earth and several nearby buildings and all the contents of those buildings, including the steel, were turned almost entirely into a dust cloud that did not burn the people on the street as it passed over them (Fig. 2C). This is not easy to explain with conventional technology, or by any process that generates intense heat. Even more difficult to explain is the odd type of fuming that came from the remains of these damaged buildings. This fuming at Ground Zero lasted for at least one full year (Fig. 3A-B). Nothing that produced a cool dust cloud could stay hot for a year, therefore the fumes were not the result of residual heat from the initial attacks at Ground Zero.