India of the past was a well sought after market for exotic goods such as spices, diamonds and colourful garments. From the beginning of the second millenium the land and sea route to India came to be dominated by Arabs and Turks, the middlemen in global trade in that part of the world.

A direct sea route to India was discovered by the Portuguese towards the end of 1490s. To European states this opened up the possibility of bypassing Arabs and Turks to conduct trade with India, which was previously an isolated market. Following the trail of Portuguese, many influential and powerful European kingdoms sent their envoys and merchants to establish commercial treaties with Indian kings. This gave birth to chartered companies such as the British East India company and its counterparts that began building a string of factories in India and the East Indies, made treaties, entered into alliances, fought and subdued locals and competitors alike.

Despite the initial headstart, Portuguese, the Dutch and the French eventually lost to the British who gradually became the overlords of the Indian subcontinent.

TLDR: The discovery of a direct and unhindered route to a prosperous market and the lure of the glamour of the Orient.