Pretty straightforward really, FED, one or more chunks from the failed gear get carried forwards by the faster rotating sun gear and get entrained between the sun and those next 2 planet gears. With nowhere else to go it pushes the 'spigots' (or carrier pins) outwards causing the carrier to bend and the ring gear to burst.
It appears to have happened quicker and with a lot more energy than REDL where 7 planets and the inner race from the 8th stayed with the carrier.
It is not clear from the other photo
(Close-up of the inner race from the failed planet gear) posted by AIBN whether it is showing the loaded arc or the reverse side of the inner race. Once cleaned up, if there is no evidence of pitting it would suggest little or no spalling of the outer race prior to fracture.