This one didn't collapse, it sank. It was essentially a twin hulled boat, held in place by proppellors (thrusters) and a fancy control system.
So the proper question was:
When was the last time an oil platform sank and the blowout protector did not work and remote submermissibles couldn't shut it off either?
“This one didn’t collapse, it sank.”
Somebody on another thread posted that it sank because of the boats trying to fight the fire dumping to much water into it.
The boat sank because the BOP didn't work and the resultant fire caused structural weakening near the wellhead with the draw works and all the drill string pipe stacked as a dead load. I'd surmise that the platform sagged enough to cause the two hulls to twist until they started taking on water.
As to the BOP, The question is where was it? Normally the BOP is installed just below the 'Kelly table' which rotates the drill string. This is certainly true of wells drilled on dry land. If there is a different practice for deep water wells it probably was located 5000 feet down on the sea floor. The pile of debris from the sunken platform and the 5000 feet of pipe could be blocking any approach to the underwater wellhead by ROVs.
Regards,
GtG