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The format of the anime as it is now comes from Ash losing the Kalos league.
He only won the Alola league because they realized from the uproar of Kalos that audiences actually want to see the protagonist win. Who knew.
And once he won Alola, they had to tackle the (entirely self-imposed) problem of what to do with him once he was a league winner. So they designed the Pokemon World Championship to be a bigger competition, which, again, Ash looks likely to win. And once he wins, yet another radical change in the format will most likely come.