Why did the people in Europe try to find a sea route to i India?

India dominated the world GDP for 1500 years form 1 BCE to 1500 AD. The GDP of India was ~ 30% during this time. The U.S. was non-existent at 0.1% and the whole of Europe was around 5-10%. So hundreds of sailors attempted to find the sea route to India but only Vasco-de-Gama succeeded and Christopher Columbus found the America instead of India so people know him too...
(GDP Source, Angus Maddison, The Economist)