Why didn’t the Greeks have a navy before the Greco-Persian wars?

In any case, building a large fleet requires very high costs in terms of resources and finances, and since Greece was not a single state, building a large fleet was an impossible task. Although Greece had a fleet before the Greco-Persian wars. Trojan War, when a Greek fleet of 1000 ships landed on the coast of Troy. True, these were mostly transport ships. During the war between the Greeks and Persians, in order to pacify Persia, it was necessary to build their own fleet and defeat the enemy’s fleet. In this connection, a fleet was built, which, under the command of Themistocles, defeated the Persian fleet.