"King of the Creatures" is not just a song that Bumpus is famous In-Universe for, it's also his only song.
It got so insanely popular because people in this world are just THAT into songs about hunting and torturing animals. Bumpus being a one-trick pony would be very ironically fitting for his egotistical personality.- Jossed: Examining the records in Bumpusville shows he does indeed have other songs to his name, at least four gold records, two platinum records and two tracks that did well enough to deserve commemorating. He is very much not a one trick pony. Just a tool.