Organization is a hell of a drug.

The mixture of an influx of wealth from stumbling on (and thoroughly looting) the Americas and the hyper-cutthroat politics of European states resulted in a literal-and-metaphorical arms race between them that led to the development of what we would regard as ‘modern’ state institutions. When Europe started poking its nose around in Asia for imperialism purposes, they had developed a remarkably robust and active state structure, while the Mughal Empire in India has just (by sheer coincidence, and bad luck for India) collapsed, while China’s Qing Dynasty was more interested in perpetuating a stagnant system that saw no real challengers since the Qing overthrew the Ming - in part because China is fucking massive and powerful, and who’s going to fuck with that as a near-peer? No one nearby, that was for damn certain.

As such, the Euros went in against China with slightly superior weaponry (flintlocks in China, for example, being less widespread than the older matchlock; but both sides still heavily dependent on the melee clash) but vastly superior military organization, officer corps, and training methods. One of the astounding things you note, reading about European colonization, is that when hand-to-hand combat is joined, oftentimes the imperialized peoples still do not have the upper hand, and are still often repulsed with inferior numbers. In the modern day, we romanticize a bit the pre-modern warrior, but the truth is that a man who has spent the past year of his life intensely drilled by other experienced soldiers is generally more-than-a-match for a part-time warrior who has intermittently trained, according to his own standards and motivation, over the course of his life - or, in the case of China, of feudal-style ‘banner armies’ which were nominally professional but lacked modern military institutions which result in professionalism.

Also, ships. 17th-19th century Euro ships were fantastic for their time, and easily blew the competitors out of the water - literally and metaphorically.