Let's also not forget that you battle him once, ONCE, and immediately afterwords he just claps, says "I forgot how fun Pokemon battles were" and completely gives up on his plan and sends you off to defeat Eternatus instead. And all to the tune of a completely unearned One-Winged Angel ripoff.

I hesitate to even call him a villain his "arc" was that much of a joke.

The main problem is they didn't bother putting in so much as a throwaway excuse to explain why he couldn't wait ONE MORE DAY out of said 1000 years to get Leon on board. Even some "it only works on this specific day because of bullshit plot reasons" line would've been a start.