They found ancient inhabitants of Georgia using iron ore as flux for copper smelting, so it's a theory of how they went from one to the other. It's not terribly exciting but it beats "they tried smelting rocks at random to see if anything good would happen".
Smelting random rocks (with fairly distinct appearances) sounds like a very logical thing to do. I would say it's a natural human impulse to experiment with random stuff and see what happens, that's curiosity.
What sound highly improbable is someone having access to this obviously different ore (used as a flux) but never thinking of smelting it.
