Further Proof 9/11 Was An Inside Job

Another high-rise steel framed building was ENGULFED in an inferno, but DID NOT COLLAPSE:

http://www.zerohedge.com/news/2017-06-14/it-just-went-fire-engulfs-london-apartment-block-least-6-dead

So why did WTC1, WTC2, and WTC7 collapse on 9/11? It was NOT because of the fires or impact damage.

Only an additional source of energy could have led to their disintegration/collapse. What was it, and who put it there?

It didn't come from Saudi Arabia. They can't even pump their own oil, for G-d's sake.