I'll just leave this little rabbit hole for anyone who might want to take a gander at more theories.
I got to talk to one of the Hawaiians who was part of relearning traditional Polynesian navigation. Lots of fascinating stuff I didn't comprehend about waves and weather. And the boats they built are beautiful.
Did he talk at all about stick charts? Those still blow my mind. Edit: My mistake. Wrong culture. But stick charts are still pretty nifty.
He talked about how much information they could get from swells, like finding the prevailing wind direction from the swell even when a storm was blowing a different direction at the time, or how islands change the swell, and he did mention the stick charts. I think that stick charts aren't useful for the very long lengths of empty ocean on trans-polynesian journeys though, and aren't as useful on a more linear island chain like Hawaii. Navigation traditions were being forgotten in Polynesia for a bunch of reasons - westernization a big part of it. All the observational techniques can't really be learned except through through the generation of experts before you. The Hawaiians stopped building boats big enough to cross Polynesia centuries before the Europeans came, but in the last century even the traditional ways to sail and navigate their inter-island boats were being lost. Read about Mau Piailug and the Polynesian Voyaging Society and Hōkūle‘a. While Micronesia and Polynesia are different cultural groups, the navigation and voyaging traditions are similar enough that the Polynesians looked in Micronesia for someone who would teach them. They found few who still knew, and Mau was the first who would teach them. I don't know if there is any way to find the differences between Mau's Micronesian navigation and the lost Polynesian traditions, but the remnants of Polynesian traditions were similar. Mau broke traditions against teaching their navigation traditions to outsiders because he he wanted there to be someone to carry on the knowledge and traditions, and bring it back to his own island if it was lost to westernization there too.