Ash may now be on the verge of achieving his dream of becoming a Pokémon Master and champion of the world, but Ash's first victory, which set him on this path, was far earlier than his win in Alola.
As the protagonist of the Pokémon anime, Ash often makes it to the final tournament in each region he visits, but his luck in winning the tournament has been infamously abysmal. In his first Pokémon tournament, Kanto's Indigo League, Ash only made it to the top 16, while pushing further to the top 8 in Johto, Hoenn, and Unova, and even the top 4 in Sinnoh. His performance at the league tournament in Kalos was his most impressive, winning tough battles with the help of his special Greninja, but there he lost in the final round, leaving him as a runner-up. It wasn't until Alola's league tournament that Ash actually managed to clinch a title from the games, and that title made him eligible for the Masters Tournament that he's been participating in for the Journeys/Master Journeys anime.
However, Ash has been to regions beyond those which have appeared in the main series of Pokémon games. The first example of this was the Orange Islands, an archipelago not far from Kanto which was the subject of a "filler" season while Pokémon Gold and Silver were in development. The season featured early looks at some Johto Pokémon, like Tracey's Marill, but most importantly featured a special challenge known as the Orange League. The Orange League featured four gym leaders who preferred contests of skill rather than battling, as well as a "Supreme Gym Leader" who functioned like the champion typically does in Pokémon games. Since the contests focused more on relationships with one's Pokémon, Ash fared pretty well, and he managed to pull out a victory in his battle against the Supreme Gym Leader, earning himself a championship trophy (depicting a gold Pokéball with wings) which can still be seen in his bedroom at Pallet Town even in the Pokémon Journeys series.
Pokémon's Orange League Foreshadowed Alola Decades Earlier
Interestingly, the Alola region actually bears a lot of similarities to the Orange Archipelago. Both regions are tropical and made up of four islands, and feature challenges other than straight battling to earn their equivalents of gym badges. The Orange Archipelago even features unique versions of common Pokémon like Butterfree, similar to Alolan forms. While the Orange Islands have never been featured in a Pokémon game, it seems the developers of Sun and Moon may have taken some inspiration from it, and it's possible that the anime decided these similarities made for a good chance to have history repeat itself. The Orange League's unconventional nature may have been the justification for why it didn't count towards invitations to events like the Masters Tournament, but none of that changes the fact that Ash actually managed to achieve a champion title over 20 seasons ago. At the time, it wasn't known if Ash would continue to be the protagonist into Johto, so letting him have this win ensured Ash's character arc would end in a satisfying spot.
The Orange League hasn't quite been forgotten today, but it happened so long ago that many younger fans may not even be aware of Ash's first Pokémon championship victory. As Ash settles in for his final match in Pokémon's Masters Tournament, it's good to remember that he has more than one title to his name, so the outcome is far from a foregone conclusion.