How could the British have successfully colonized most of India but?
The truth is, the British found it was too distant a country for them to fully colonise. At the very beginning, the British started by colonising part of North America, and they told themselves, well, China is not far ahead, we only have to cross the Pacific Ocean to get it. Anyway the British certainly were no better than ancient Polynesian seamen who already conquered the vast ocean between Asia and America. The British stopped at the eastern coast of North America. Not long after that, the British made their attempts along an eastward route, on their way to this exotic oriental land, they were stranded midway on a continent they later called India, the British told themselves, well, China is nor far ahead, let's have a rest here in India, it's tea time! However, the British certainly had underestimated the hospitality the locals offered them. With a good treat of a tea meal, and a white, afternoon sun that made people sleepy, the British stayed momentarily in India. Decades later, finally the British arrived in China, but their attempt to attack China simultaneously from east and west failed since the birth of the United States gave the British a hard kick to the bottoms and blocked their way further to China. As for the Japanese, they were in a much worse situation, confronted by three major powers with China from the west, the US from the east and the British from the south. The Japanese proactively fought on multiple frontiers, just like Germans did in Europe. Without doubt, it was only a matter of time for them to refrain from being arrogant and return to the reality. It just did not work.