So you watched the video and hopefully learned that internal structural failures led to its collapse. We also know the building was on fire. We know that the debris fell on the building and could easily have penetrated the roof causing unseen internal damage. We did not see any evidence of explosions before the building, including the penthouse, started to move. There is no requirement for explosives to account for the collapse of the building. All it takes is for one beam to fail. The loads that beam was designed to carry are transferred to adjacent beams which are now overload and side loaded so they start to fail. It was not a pancake collapse, it was a progressive collapse taking some 15 seconds from start to finish.