Columbus did not discover India, but he discovers the New World, where Europeans could build colonies, increase their populations, transplant their culture, and get supplies and wealth, uncontested by Muslims. Others did discover trade routes to Asia.
This invigorated Europe, helped cause the current age of science and trade which eclipsed Islam, and not until now was Europe threatened by muslim invasion.
***The reason Columbus is important is he saved European Civilization from falling to Islam***
It was inevitable that the New World would be discovered at this time. If Colombus had not discovered it then the Portugese would have a few years later when they found Brazil while heading for India around Africa.