I don't understand the arguments people are making that this is somehow grave robbing. Grave robbing you open up a grave and steal the personal artifacts and possibly the bones of the person interred there. Archaeologists have done a lot of this over the years and that activity is definitely grave robbing. It's a bit more restricted now in the US due to the NAGRA that restricts messing with human remains in some contexts.

In this case though the salvagers are not taking the bones out, nor the personal effects. They are taking huge amounts of steel, brass and copper, none of which were personal artifacts or property of a single one of the persons who died at the site.

To call this grave robbing, then removing a wrecked bus or truck from an accident site on the side of the freeway would have to be considered grave robbing as well. If the person removing the bus also took the body, wedding rings and gold teeth of the victims, that would be a crime. But the person removing the bus isn't doing that.