Mystery behind Moana: After 1,700 years, why did Polynesians suddenly sail east?

An increase in the supply of boat snacks?

This talks about climate impacting the population, but it made me wonder if herd immunity to disease in an isolated population could cause population limiting diseases to go extinct after awhile.

Why does anyone do anything? Some people obviously just got really into the idea of sailing to the islands.

Right now there are people in the world that are super into the idea of going to Mars. There’s no reason why anyone has to do it, but they’re into the idea of it and they’ll find whatever rationale they need to explain the desire.

Same reason as everything - looking for women

This was covered in the movie.