Interesting.... I would guess the throw out bearing was in constant contact with the pressure plate and thus spinning 100% of the time. Which led to throw out bearing failure. Surely it would have been making a LOT of noise when it first started to go out, but nothing was done. It must have eventually "locked up" from the overheated bearings and then the entire assembly started to spin? Ripping off the retaining ears that secure the bearing to the throw out arm. The noise must have been very loud and terrible.
It is controversial whether a throw out bearing should or shouldn't remain in constant contact with the pressure plate. The problem is, there is no "one" answer to the question. Some setups, some throw out bearings, are designed to run with constant contact to the pressure plate, some aren't. This throw out bearing and setup appears to be the later style. As for me, I setup ALL throw out bearings for clearance so they DON'T constantly spin with the pressure plate. Some folks think it's to much work, to complicated or not needed. They could be right, but this top loader says there not!
It might be that you need to make SURE you get a throw out bearing specifically designed for constant contact. Some are, some aren't. If you don't get the right one, you may well suffer the same problem again. Or, do what you gotta do to make sure there IS clearance. But do one or the other, the right bearing or enough clearance, it's the only way to be sure the problem is solved.