And the only reason there's a Dethklok here at ALL is because... y'know. Dethklok was here. Repeatedly.
Before they showed up, there was a cartoon show called Rockageddon and it starred the multijillionaire death metal band, The Death Clocks.
But yes, the whole jamjar scenario is what makes this place work. It's why Irk doesn't exist, and even if it does exist as Urk, the Urkens won't be sending Zam here for another like, 200 years ANYWAY. So yeah.