Which phenomenon most contributed to the rise of both the minoan and mycenaean cultures?

Use of naval trade-- The Minoan and Mycenaean civilizations used their naval technology to travel the Mediterranean Sea and make contacts with area empires for trade.

There is even evidence the two civilizations may have made contact with one another leading to the Mycenaean conquest of the Minoans. Trade led to an exchange of ideas, technology, wealth, and eventually allowed both to grow through conquest of trading areas.