In the centuries after the two groups separated, they evolved in opposite directions, the North Island Maori developing more-complex and the Moriori less-complex technology and political organization. The Moriori reverted to being hunter-gatherers, while the North Island Maori turned to more intensive farming.
it's not necessary that change is always from hunter-gatherer to farmer. some people reverted "back" to being a hunter-gatherer after having been a farmer