I think poaching of trophy animals and the impetus to have fenced encloses where people can shoot bull elk and other big game (turned into livestock) comes from the same motivation–get those antlers by “hook or crook.”
The increase in poaching may be due to the underfunding of wildlife law enforcement. The New York Times article below suggests that, and I wouldn’t be surprised if some of the biggest poachers, or those involved in facilitating it, are local political leaders in these states, thus explaining in part the poor funding for law enforcement.
New York Times. Poachers in the West Hunt Big Antlers to Feed Big Egos. By Randal C. Archibold.