A Rapid spread of Polynesians

At www.hawaii.edu/news/article.php?ald=4097 … is a news release of a reappraisal of the timescale of Polynesian migration across the eastern Pacific via a study of 1400 C14 samples from 47 different islands. Polynesians were in Samoa by 800BC but the colonisation of the islands further east, such as Hawaii, Easter Island, New Zealand, the Societies and Marquesas etc took place within a period of 200-300 years, first reaching the Societies by the 10th century AD. Why at that point in time might be one question. As it took place in the Medieval Warm Period we may assume populations grew as they are always inclined to do during optimum climatic phases – but is that the sole reason? What else might have been going on?