We are shown Luffy truly living up to his heroic reputation in this post-victory episode by means of his complete lack of pride or hubris. In the wake of saving Cocoyashi from the reign of Arlong, the Straw Hat captain has no desire for rewards or payment of any sort except for lots and lots of food, which is ultimately just a bare essential human need. The thought of exploiting or extorting anything else from this village is absolutely foreign to his wants & desires. Then, when Genzo threatens to kill him if they ever hurt Nami, instead of being angry at the accusation or arguing that he could defeat Genzo, Luffy only acts shocked at the thought of ever trying to hurt Nami. Even as they are departing and Nami is pickpocketing the crowd and jumping to the ship without saying goodbye, Luffy just shrugs and admits that, though he is the leader of the crew, it’s “not [his] decision, she does what she wants.”
I appreciate the notion of nurture outweighing nature when Genzo says to Nami & Nojiko “you certainly are Bellemere’s kids.” Bellemere only raised the girls for a few formative years but her impact on their personalities is clear & remarkable. As the girls come from a distant location, they likely lack many genetic similarities with their surrogate parent, but their relationship is still apparent.
When Bellemere delivers the line “you need to learn to be strong girls who smile even during hard times; do that and nothing will ever stop you,” it continues to push the consistent One Piece philosophy of maintaining a jovial attitude regardless of outside circumstance. This zen approach to suffering is a recurring trait within all of our protagonists and has a strong impact on the compelling nature of the narrative. An even deeper interpretation suggests that Bellemere, still smiling during the difficult time of being dead, would not let anything stop her from still pushing Nami out the door towards the next adventure the horizon may bring.
Last note, yet another nod to reputation, the larger purpose behind Nami stealing the wallets from the villagers is to let them have an interesting story to tell about the day she left. After 8 long years of oppression, the story of the Straw Hats arriving to bring freedom will go down in their history for generations, and a big part of that story will be how the local girl who brought the friendly pirates to their shores pickpocketed them instead of saying goodbye or letting them thank her. It is, of course, only a mild inconvenience to the villagers who have been left with the 100,000,000 berry fortune Nami had accumulated (which Luffy also had no interest in), but a striking note in the legend to be told & retold for decades to come.