Greece is very hilly so it was hard for the ancients greeks to farm the land and use crops as a main source of food so instead they use sea food as a main source of food since they are sorounded by the ocean.
The importance of spreading the faith was to save Indians from heathenism and prevent them from falling under the sway of Protestantism. Enslaving the Indians was justified as a means of liberating them from their own backwardness and savagery and enabling them to become part of christian civilization.