Of course they didn't. What you saw was mostly burning Jet-A. Almost anything will burn if you get it hot enough, and what doesn't burn first, will melt or weaken, as did the structural steel of the building. That, plus the damage caused by the impacts, caused the collapse. The images I saw today appear to have been cleaned up in some way, than what I'd seen earlier. You could cleary see the collapse start at the place where the a/c hit, and the weight of the floors above caused the structure below to fail, then that slamming into the floor below it, did the same to it, and so on to the bottom , when the sudden stop probably caused the upper floors to finally join their lower "brothers" in collapsing. Similary for that video that started as some sort of training or documentary from Gamma Productions?, something like that of the first plane boring in. Before today I coudl never actually see the airplane, just the dust and then flames. Today you could clearly see the aircraft itself.
Thank you. It's what was going through my mind before I knew any better.