One of the floats was damaged by something during the explosions. Jagged pieces of steel would be shot like bullets in all directions.
Remember, it wasn't just the oil, it was also the fuel in tanks for the generators, and barrels of fuel stored to use in the generators, and any other gas or diesel powered motor.
Once it was on fire good, there was no power, so bilge pumps were not operating.
It became just a matter of time before the rig listed over and sank.
So the living quarters...are they on other platforms connected to the rig? That doesn’t look big enough to house the workers. As you can tell, I don’t know much about rigs etc.