It's just speculation on my part, but perhaps this is exactly what led the parents, police & prosecutors to conclude unanimously that it was the victims' late model Toyota 4-runner sticking out like a sore thumb in a derelict neighborhood which attracted these psychotic predators to their victims in the first place.
Or it was the fact that they were white.
I'll even consider that the fact that they were white led the perps to believe they might have more to steal. So while they may not have acted purely out of racial hatred, the victims' race would still be a factor.
And if they were just after the victims' vehicle, why the kidnapping, rape, torture and mutilation?