>As for why it was lost. The article speculates that it was climate change, but I think the lack of a system of writing is probably even more to blame. Some disaster kills off the school of deep ocean navigation and the skills are lost as the old sailors die off.

I think it's a bit more complicated than that. When James Cook came through Polynesia, he brought syphilis which ravaged the populations of Tahiti, Hawaii, and others - weakening oral tradition of passing down information. Also, when europeans first came, they were overall very un-interested in preserving any oral history, and mostly just colonised and fucked over the local populations - playing out the classic tropes of colonisation.