It was large enough to maintain a settlement. It was defensible. It lay near the mouth of the most vital river on the North American coast, and so served as a waystation for traffic coming from the fur-trading areas to the north. It was the natural place for the capital of the colony of New Netherland.
Of course, Indians knew of it long before any Europeans arrived. The Mohawk called it Ganono, meaning "reeds," no doubt because of the reedy marshes that surrounded much of it. But the Delaware name--variously recorded as Manados, Manahata, Manahtoes, Manhattos--is the one that stuck. It meant "the place where we get bows," or "the place where we get the wood to make bows." The Dutch settlers picked up the name and used it. And the rest is history.