They were isolated because they were often far away from each other and were independent of each other because a united Greek state didn't exist, they were all independent city states. Many of them were also on islands that were inaccessible by normal means. Roads were not as developed because of the many islands and rivers and things like that, so they developed in isolation.
Ancient Greek communities were isolated due to their mountainous geography and the structure of self-governing city-states called poleis. Each polis developed independently, fostering local loyalties and limiting interaction, despite shared language and culture. The geography and lack of a unified state were the primary reasons for this isolation.
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