Why is posedion the ruler of the sea?

In the earlier period of Greek civilisation, the Mycenaean culture, there was no connection between Poseidon and the sea, even though this culture flourished on an island (Crete). He was seen as the king of the underworld. Later, the poets Homer and Hesiod suggest that Poseidon became lord of the sea when his brother Zeus overthrew their father, Knonos (time). The three siblings then divided the world among themselves by lot. Zeus was goy the sky, Poseidon the sea and their sister Hades the underworld. They shared the earth and Mount Olympus.