But then you have to retcon the fact that Rion was buried or was dug out again by someone
I still dunno how to feel about it and I hope there is a better explanation. After the Thailand arc (Peak) things weren't as serious toned until that Nakamura sniper dude shows up in beginning of the Museum arc.
There is so much potential man, they even teased other Assassination Associations around the world, notably the France one where Sakamoto assainates that perverted disgusting painter assaassin.