Urbanization increased in the hellenistic world because:

Thanks to the navigation and improvement of ships, the people of the Hellenistic world had the ability to trade with other countries, something that gave them a great maritime economy and new possibilities to expand their own cities, filling the resources and materials, to put an end to the Bronze Age and make the State Cities a common way of living for the people of ancient Greece. This development of commerce and navigation made it possible for cities such as Crete to have an accelerated hubanization, since they changed the agricultural way of life by a trade-based economy, and were influenced by other countries, in addition to the new riches that they they could get.