The Pokémon anime was established back in 1999 and quickly formulated a plan where the series progressed through the various Pokémon generations like its game counterparts. Ash Ketchum and Pikachu led the way through each region, catching local Pokémon, taking on Gym Leaders, and progressing toward the Pokémon League in the process. This became the essence of the Pokémon anime's identity through Kanto, Johto, Hoenn, Sinnoh, Unova, Kalos, and Alola, even if the latter chose to focus on its Grand Trials over Gym challenges.
Source：https://www.cbr.com/pokemon-journeys-failed-galar-region/
