There are many possible scenarios to this, and all well known and understood by the manufacturer. The evidence is in the remaining parts both the disk and the engine.
Friction is not enough to fail the disk, an oil fire is
The B747 QF that occured out of LAX failed in the same area but tangled the blades and vanes together adding both a braking action as well reducing the driving torque.
Other features at play would be the stretch of the disk either being absorbed partially by the case or releasing the blades from their slots and significantly reducing the load on the disk.
Taken together in light of the well demonstrated tolerance of the Rolls design in the earlier QF incident the loss of the disk in the A380 was a surprise. The rotor hardware is not easy to change so my bet is that the final fix will be on keeping the oil where it belongs.