Theory: Ash lost in Kalos, so TPC could make him win in Galar, canonically one of the strongest leagues and hardest league, and the best feel.

The win for final battle between Ash and Alan was very close. He could've won, and it was anyones finale. It was purposefully made like this, so they could decides last minute who would win.

The final battle aired in japan Aug 2016. 5 months later the switch was released.
It is reasonable to believe the Pokemon Company/Game Freak seen and knew the switch about this time and before then.

And Sword and Shield released 2 years later, as usual for pokemon games on consoles once released.

My theory, is they decide to make him lose this league once again.They knew Sun and Moon was gonna be a sorta holiday region. The gym challenge, if there was one, wouldnt have the same respect as kanto, sinnoh, or kalos.

And they also at this time, already were drafting plans on making a UK-inspired region where football stadiums would be the gyms where fans watch battles. It would be very epic, and would show even better in the anime. Fans would want nothing more than to win THIS one.
But we didn't know what Game Freak was planning in 2016/17.

So TPC made him lose, but were safe in the knowledge that Ash will kill in the Galar region, and becomes a celebrity.

But fan hate grew so much, they made a champion of him in Sun and Moon, and placated themselves with the knowledge that this series is just a holiday spin-off and an offbeat to the rest of the franchise.

And now Ash is gonna with the Galar league. Thoughts?