Probably b/c there is a huge bullet hole in it.
On the contrary, bear can be very good eating and many people enjoy it, including myself.
Leaving the head doesn't mean anything. A licensed bear hunter is just as likely to leave the damaged skull as is a poacher, and the hunter apparently took the hide and meat.
But really, who knows and who cares; but jumping to the conclusion that it was poached is stupid, espescialy when its the middle of bear season and its easy to get multiple bear tags.