What drove the Spanish and Portuguese sailors to India? Which of them managed to open a sea route to Asia?

Although even during the reign of Alexander the Great, the Roman Empire and Byzantium, trade between the countries of Europe and Asia was carried out by land, with the advent of Islam and Muslim countries between India and Europe, the way to Asia for Europeans was lost. And Indian and Chinese goods such as spices, precious stones, handmade fabrics, etc. in Europe they cost more than gold and attracted Europeans. The Portuguese were the first to reach the Indian shores by sea (the voyage of Vasco da Gamma at the end of the 15th century).