Everybody discovered it. Some discovered it and lost it, some came here and didn't know they had discovered anything, some visited here often and just didn't tell the rest of the world, and the 15th century explorers discovered it for the people who are the progenitors of our current world wide culture.

It's like who discovered the wheel? It doesn't really matter that Grunt and Ook invented it 30,000 years earlier, the invention of it by the people who made it into a world changing tool are the ones who matter. So Grunt made a wheel, used it to carry firewood until he broke it and left it lying on the side of the path. That takes nothing away from the people who learned how to make them and built a civilization around that knowledge.

Marketing, it's all about marketing.