The building collapsed because there was no reo in the bottom left side witch separated causing the first stage of the collapse, then twisting the remaining part of the building causing the floor to disintegrate and fracturing the floor slabs and exposing the reo making the building to twist which caused the rest of that section of the building to collapse. Maybe a second fault of no reo stopped the remaining building collapsing.
This is just a report on just seeing the video footage. Lets see if I am right or is there going to be a cover up.