Why did the Manchu people die so quickly in Bi Meng?

The first step is to establish a supranational military group similar to the "flag bearer" to objectively help Chinese spread within the group. In the second step, most Manchu speakers will stop living together and live together with Chinese speakers on a large scale, which will help to spread and infiltrate Chinese again. Thirdly, in Jilin and Heilongjiang, where Manchu people live in concentrated communities, China immigrants entered on a large scale at the end of 19, completely ending the Manchu-inhabited communities. In fact, the third step is bound to happen. Different from the semi-arid areas of Mongolia, the Nuzhen language in the northeast and Ainu language in Hokkaido are both forest areas with fertile land and abundant rainfall. /kloc-in the 6th century, high-yield crops flowed from America to the world, and then the farming peoples in East Asia went to population explosion. /kloc-at the end of 0/9, on the one hand, there was huge population pressure, on the other hand, Russia's gradual advancement. A farmer from China and Honshu, who got married and had children, went north to immigrate to the border, which is an inevitable result. In human history, all ethnic groups have been in a state of mixed living and serious population disadvantage. There are few such examples, including only some Abrahamic monotheistic peoples. There are also Chinese in Muslim countries in Southeast Asia (like Thailand, the Chinese have almost disappeared).