They don't.
It is just that Nami and Crocodile are representatives of Wealth.
And they will be fighting for Wealth, the treasure One Piece. The winner gets to take it and become Wealth.
Fame is a fight over PK title - the ultimate Fame in this show, Buggy vs Luffy.
They happen to be representatives of Fame.
All according to keikaku.
It is just that Nami and Crocodile are representatives of Wealth.
And they will be fighting for Wealth, the treasure One Piece. The winner gets to take it and become Wealth.
Fame is a fight over PK title - the ultimate Fame in this show, Buggy vs Luffy.
They happen to be representatives of Fame.
All according to keikaku.