Why does Qin have so many war resources?

First of all, Qin seldom suffered a big defeat after filial piety, but gained a lot. Secondly, the better policy environment brought by Shang Yang's political reform has brought many immigrants. Thirdly, the territory is getting bigger and bigger and there are more and more people. In fact, during Qin Shihuang's unified war, the cultivated land and population of Qin State were not far from the sum of the six countries. Finally, the productivity of Qin is more developed than that of the six countries, and the unit land and people can supply more troops.