Certainly they had to have a well-founded philosophical and legal tradition, in order to effect a constitution and rule by law (rather than rule by personality). There were silver mines throughout Greece allowing the city-states a developed economic system allowing for a treasury to fund defense and public works. The cities were mature enough to have a forum, a meeting place where those with political voice (adult male property-owning citizens) could debate and make their voices heard. And the class system in the Greek city-states allowed enough leisure time for the voting class that they could partake in such debate.

That’s all that comes to mind. Hope this helps!