What led to European kingdoms trying to find a water route to Asia for trade?

By the 1400s, Ottomans controlled the overland route to Asia and charged increasingly high tariffs to Europeans traveling through to countries such as India. The Mediterranean also became more and more dangerous and prone to piracy from groups such as the Barbary pirates, who would capture and enslave Europeans.
While the spice trade and trade in other goods from Asia, such as silk, was extremely lucrative, the tariffs and the risks of the overland route began to outweigh the benefits. Europeans especially desired the spices that came from India and were willing to pay very high prices for them, but there was a limit on high they were willing to go—and merchants needed good profits to incentivize themselves for the risks of what was then somewhat akin to what a voyage to Mars would be today.
Therefore, Europeans became increasingly determined to keep exploring until they found an ocean route to India. Vasco de Gama finally discovered this route in the late 1400s when he managed to sail around the tip of Africa and across the Indian Ocean. This was a long and dangerous voyage, but the lack of tariffs and pirates made it very lucrative for merchants.