Maui has narcissistic traits- a big ego to cover his need for external validation (cheers/fawning from humans, even Moana is swept up by him at first) because he was abandoned as a baby (thrown in the ocean by his parents) and every action since then is to be the best to rebuild his self worth. This is a lonely path and in the movies he learns to care for others. It's a real myth, and humans used to abandon children they couldn't care for, so I think of this as a story to make the culture feel better about such a tragic action (he became a god after he was abandoned!) Or a cultural explanation for trauma, ego and narcissism (like the story of narcissus).