Need to pick up one piece again

We now know that the world of the past is now submerged deep in the ocean.. and we all expect all this to be the aftermath of WG/Allied Kingdoms fight vs Joyboy and his crea.

But what if it was the work of the Poseidon of that time instead? Back in Fishman island arc, Otohime stated that this power can actually achieve that, and I don't think Oda put that piece of lore just to show the antithesis of "using power for good/bad"