Why were Spanish and Portuguese rulers in particular so respective to the idea of funding a maritime quest?

European economy went through the phase of a decline from the mid-fourteenth to mid-fifteenth centuries. Due to plague and wars, a lot of people died in various parts of Europe. Trade became slack. There was a shortage of gold and silver, used for making European coins. In the late fourteenth century, long-distance trade declined, and then became difficult after the Turks conquered Constantinople in 1453. Italians established their business with Turks. They were now required to pay higher taxes on trade.

The possibility that more people could be brought into the fold of Christianity made devout Christian Europeans ready to face adventure. After this, ‘the Crusades’ against the Turks began as a religious war. They increased Europe’s trade with Asia and created a taste for the products of Asia, especially spices. Its trade could be followed by political control, with European countries establishing colonies in regions.

Gold and spices were found in new regions. Portugal was a small country which got independence from Spain since 1139 which had developed fishing and ailing skills, took the lead. Prince Henry of Portugal attacked Ceuta in 1415. After that, more expeditions were organised and the Portuguese established a trading station in Cape Bojador in Africa.
In Spain, economic reasons encouraged individuals to become knights of the ocean. The memory of the Crusades and the success of the Reconquista fanned private ambitions and gave rise to contracts known as Capitulacion.es. Under these contracts, the Spanish ruler claimed rights of sovereignty over newly conquered territories and gave rewards to leaders of expeditions in the form of titles and the right to govern the conquered lands.