Several European nations, most notably the Portuguese and later the British, were able to take over trade in the Indian Ocean? I'm aware that the takeover involved violent seizing of crucial trade cities, e.g. Goa. Why were the native Indians, Arabs, and South East Asians who had traditionally controlled the trade unable to effectively fight back? Is the answer simply: The Europeans had bigger boats and fewer scruples?
The first European power in Asia was the Portuguese.
How did this small European nation come to dominate the Indian Ocean trade (and eventually the Western Pacific trade) to such an extent that it undercut the ancient Spice Road overland from the East to Europe?
The key technology was naval. The combination of Mediterranean and Northern European shipbuilding, with the addition of powerful cannon, created a unique new naval technology. Ships which were strong, seaworthy, and powerful. This technology was difficult to copy.
The Portuguese consolidated their domination of the Indian Ocean trade in the Battle of Diu in 1509. In this battle, 12 Portuguese carracks and 6 smaller caravels defeated 92 ships belonging to the allied powers of the Gujerat Sultanate, the Mamluk sultanate, the Zamorin of Calicut and the Ottoman Empire off the coast of India.
European Carracks were invincible by previous maritime technologies. This Battle gave Portugal control of the Indian Ocean (not uncontested, the Ottomans made several later -but unsuccessful - attempts to defeat them).
Naval power, and naval technology was the key to European domination of the globe. It was especially important for the earliest European colonists into Asia.