Why was portugal the first european country to embark on an exploration program?

In the second half of the fifteenth century began a territorial expansion driven from a European court, the Portuguese. The reasons were due to the fact that they had seen their expansion to the South of the Peninsula closed by the conquests of Castile; so that only one "natural" path remains: the sea. Until the 16th century the Portuguese kings made serious attempts to conquer Morocco, a project little thought given the strong settlement of the Islamic civilization on the other side of the Strait. In this effort there was more than the desire to continue the "Iberian Crusade". Africa promised riches without number to the conquerors; above all, gold. In fact, the vast majority of European currencies came from Africa, so it is clear that the main reason for the start of exploratory expeditions is mainly based on obtaining wealth and territorial control.