Luffy is so fascinating when you examine him through the lense of a "chosen one" narrative.
Bc, let's be clear, the Nika fruit literally chose him. Zoan types have a will of their own, and it had been hiding for 800 years, when it suddenly picked this snot nosed kid to bestow it's power to
And at first, it seems like a really cliche, boring writing choice, right?
Bc one of Luffy's biggest strengths as a character was how he wasn't special. He's just a guy who wants to go on adventures with his friends. And even after his family is revealed - well, Garp and Dragon have so little to do with him that they barely even matter. Each of them are just doing their own thing completely irrelevant to the others
But it turns out Luffy had been special all along! He's actually a god! What a boring twist.
Except... That's not exactly the case here.
Most "chosen one" narratives have the character be special from birth. They have unique, special powers no one else has, or they're a reincarnation of some greater thing, or they're the last of a special bloodline of people, or they're a natural born prodigy, or they're secretly part demon/monster, etc.
None of these things are due to the character's own choices. These are things outside of their control and just happen to them. They're chosen to be special for plot purposes, and a lot of the time, the focus is on how the character deals with the unique hand they've been dealt with.
This is not the case with Luffy.
Throughout the series, intentional or not, Luffy has saved countless lives and become a symbol of hope and freedom for many, many characters. He values freedom deeply, and will fight to the death to help those he cares about, regardless of the consequences. And he's done it all while being an absolute fucking goofball and never forgetting his sense of fun.
None of these traits have anything to do with his devil fruit powers.
Luffy was chosen by the fruit not because he was born special - but bc his personality, beliefs, and actions demonstrated, without question, that he was exactly the kind of person that the Nika fruit had been waiting 800 years to find.