There is a curious legend, placed in surprisingly recent times, of an Alolan tournament attended by the world's gods. Although a team of guardian deities reached the final, the champion used no gods at all, but a team of mortal pokemon based around an Alolan Muk. So angered were the gods by the manner of their defeat that they cast a curse upon the tournament, and Alola, heeding their warnings, has held no tournaments since that day larger than the Island Trials and the Battles Royal.
In truth, politics always had more to do with Alola's longtime failure to host an official League than this etiological myth of a curse, although it is true that recent sightings of Tapu Koko and Solgaleo were treated by the Kahunas as divine permission to start the League, and that the former tried to assassinate the first champion after their victory. If pokemon competition in Alola is truly cursed, it was by a curse named "distance", one placed at the time of the archipelago's creation. But the Alolan Muk does possess the remarkable ability to shut off the unique abilities of many pokemon, using the noxious mixture of chemicals in its own body to reduce battles from contests of strategy to ones of raw physical strength. The famously bulky Muk and its carefully selected teammates thrive in these matches, which frustrate humans as much as they were said to frustrate the gods!
Muk has not dominated the Alolan League to the degree it has in the legends, for the pokemon trained by mortals are not nearly as frequently subject to the unique powers of its strange alchemy. For most mortal pokemon are gifted with a perhaps greater power, or at least one which counters Muk's own – a power named evolution!