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Historically Greece has been a major spot for innovation for the fields of philosophy and technology. Ancient Athens' statecraft is considered to be the foundation of modern Western democracy, but other Greek city states have also influenced European governance and thinking.Bloom
Greece's city states were culturally similar but competed and innovated, not being constrained by religion or some larger empire threatening them, these small states could openly experiment with rule. This resulted in a diverse and strong political culture where cities were constantly working to one-up eachother. This innovation was helping cause overpopulation in limited Greece, so some decided to set up colony cities which had the unintended effect that wealth was being into Greece proper through mutual trade.
This already competitive culture allowed for schools of thought to be opened where citizens (free, male, culturally greek) were actively encouraged to think freely.
Romans
Much later, Greece was subjugated by the Romans. The Romans saw how advanced Greek culture and technology was, especially on the fields of maths, geometry and physics and started adopting its architecture, religion and its societal norms. Rome had a real inferiority complex surrounding Greece, and the people of Greece reciprocated this gigantic praise by calling themselves Romans aswell after Rome granted all free, Greek men universal citizenship.
Christianity
When Rome adopted Christianity, Greece did too. The New Testament called "Hellenes" (today Greeks) pagans. The now Christianized Greeks, of course, didn't want to associate themselves with paganism thus reinforcing the Roman identity.