Why didn't the people run back to Shanhaiguan after the fall of Northeast China?

At that time, the Japanese built Manchuria according to their own national standards. They didn't destroy it, nor did they slaughter the people of Northeast China, but they engaged in the * * * of five ethnic groups. At that time, quite a few Northeasters worked in Japanese enterprises. When my grandmother was young, she worked in Jinzhou Textile Factory and was paid on time. At that time, the security in Manchuria was very good, and everyone had food. Why did she go to the customs? In fact, life outside Shanhaiguan is far less than that of the older generation in Manchuria and Northeast China.