Portugal had 2 major advantages over other exploring countries. First of all they had Prince Henry's navigation school in Sagres Portugal. This allowed them to train people in navigation, map making, and other things of that nature. This made there sailors much more efficient at sailing the open seas. The second reason was that they had easy access to the Atlantic. This allowed them to get sailors in the ocean much quicker than other exploring countries.
I hope this helps you out.
