You are a total idiot about history. Chinese defeated numerous minority armies. Most famous of them are Huns, Turks, Mongolians. All the three minorities later invaded Europe and caused big disasters there.
For Mongolians, you guys only know the glorious Mongol Empire. But it's only small part of Mongolian history. Before and after Mongol Empire, Mongolians were trample by Chinese. They were sold to Chinese as slaves. In Ming Dynasty, there was a policy called "减丁政策“, which means "periodically reduce Mongolian manpower(by slaughter)".
Even in the Mongol Empire, Chinese were the one who resisted Mongolian army for the longest time. Chinese even killed Mongol Emperor in battle field, which by the way indirectly saved the West.
For Manchus, they got their rule in China by luck. When Manchu was rising, China was suffering plague, famine and peasant uprisings everywhere. When China's capital was captured by the peasant army and the emperor hanged himself, Manchus were still staying outside of Great Wall. But after the famous general Wu Sangui(who was the Great Wall defender) surrendered to Manchus, everything changed. Another fact, Manchus had the world strongest cavalry at that time. Later they defeated mighty Galdan and Russia.