The aliens showed them the way. ;')
For years I have been struck by the extreme overweight in some of the Hawaiians shown in screen and TV, especially with some of the rulers. I was reading some books on dieting the other day, and it suddenly occurred to me that people with the capacity to put on fat, and have difficulty loosing it would be most likely to survive extremely long sea voyages where failure to find land timely would result in many dying. Thus, not only were those most efficient at fatness be most likely to survive, but also most likely to end up being rulers.