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I haven't watched the anime so I can't comment on that, but there's an old saying of "show, don't tell" when it comes to writing. In the Galar games, the text keep saying that Leon is the strongest, but it's not what's shown in the game because when you face him he's nothing special at all. It's really anti-climatic. There's also several scenes in the game where they have trouble with dynamaxing Pokemon and Leon goes off to take care of it while you continue your journey, but it happens completely off-screen. We don't see Leon fighting those Pokemon which could've been used to show his strength. The only time you see Leon's strength is at the beginning of the game when he beats a random trainer... OK, cool but anybody can defeat a random trainer.
Cynthia is the opposite, the game doesn't mention her strength at all, but when you face her most players find her team quite powerful, so she feels more powerful in the eyes of the player.
If I can make a comparison, it's like when a TV show character is described as "smart", but the writers themselves aren't smart, so the characters end up doing dumb shit that only works because of asspulls. On the other hand, there are several characters that aren't directly called smart, but do make smart decisions.
Similarly, Wallace is a "champion", but it doesn't feel earned at all because it looks like he only got the title because Steven abandoned it. Meanwhile Iris, who is in a similar situation as Wallace (8th gym leader who became champion in the next game) feels more earned because we see her defeat Alder and rightfully earn the title.