I think that Moria from a long time ago must not have been as vicious as he is now, and he must also have a group of happy companions like straw hats. However, his team was not as lucky as the straw hats, and suffered a change, and everyone died or left. This is definitely a big blow to those who regard their partner as their second life.
Just like how heavy everyone was when Usopp wanted to leave the group; just like how sad everyone was when Golden Meli left. What's even more unfortunate is that there is no more partner left by Moria's side, unlike the skeleton, and the fetters of the big whale.
So Moria hopelessly went astray and could not turn back.
His tragedy is not ambition. All people want to be One Piece, some are bloody, some are cruel. He was just a wayward kid who was left alone in this world and wanted someone to accompany him.
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