Civilisation started there because they had, however limited by area, places with extremely good soil fertility that allowed agriculture to appear there first. Agriculture meant excess production, excess production meant possibility to have organised society by using that byproduct to feed priests/military/bosses, that in turn organised system of laws and their enforcement, and jumpstarted development. Quickly they realised that flood control on rivers greatly increases availability of fertile land further improving their returns, and that required centralised control - so they had both ability, and incentives to build centralised states.