It would seem that the wheel is ONLY supported by the studs and makes it easy to see why the failure occurred. On the Land Rover the centre of the wheel is an annoyingly (when your changing wheels) tight fit over the hub. This means that the studs are only transmitting the force required to turn the wheel and not the forces generated by bouncing around on rough roads. The camper on the other hand has only the studs to support the forces generated by the crashing and banging over the corrugations and stones of the outback. After reading the referenced thread I reckon this is a failure of thinking in the design stages of the camper.
I’ve read and heard of this happening to other campers/caravans and some cars / utes / four wheel drives so perhaps this could be the root cause ?