Why did Greeks create democracy?

First of all, we should note that only Athens and a few other Ancient Greek city-states were ever democracies. The vast majority of Ancient Greece was ruled by monarchies or oligarchies and not by elections.

However, Ancient Greece was the first place that a form of government in which the governed needed to consent to laws and norms, e.g. a democracy, took root. As a result, people, appropriately call it the first democracy.