The idea that written history is an objective record is something that is loved by modern academics. In places that aren't seen to be "that" important, local social factors can affect what gets recorded. The Russians rewrote their history books. Britain still omits from its education system bits of history that are inconvenient or uncomfortable.
Re: the population being self sustaining, not really. There is a fair amount of inbreeding that is visible in the population but not enough to sustain the population and keep the island running.
Workers are imported and are left to do their thing. Higher incomes or high net-worths are a legitimate target - not just for the financial benefit but for sheer entertainment of the pedigrees.