This theory is substantially less likely for a few reasons:

* The predominant oceanic currents in the South Pacific around Rapa Nui come from Polynesia, not South America. So you're not likely to be drifting towards Rapa Nui. Indeed, traveling from Polynesia to South America via Rapa Nui isn't a particularly far-fetched idea.

* Polynesia, and earlier Austronesian antecedents, had a much stronger tradition of long transoceanic voyages. (Austronesians crossed the Indian Ocean and settled Madagascar before Africans set sail from their own coast to reach it).

What is more likely, a culture renowned for its seafaring ability and resiliency on tiny islands exploring far beyond their homeland, or a group from a resource rich continent leaving and reaching far despite their lack of experience with naval navigation and at-ocean life?

I would put my money on the islanders being the explorers rather than the mainlanders.

That was Thor Heyerdahls theory and he proved it possible with his Kon Tiki expedition but I think more recently DNA testing has shown that islands (including Easter Island?) has been settled by people from Asia.

(Writing this I realize you might have meant that people from South America went to Easter Island and back, but as far as I know there hasn't been found traces of a strong culture for navigation in South America.)