Didn't Han Chinese enter Northeast China in Qing Dynasty? Why are there so many there?

Now that technology is so advanced, there are still illegal immigrants. What's more, after the end of the Qing Dynasty, the Qing Dynasty gradually relaxed the ban on the Northeast, and people from Henan, Hebei, Shandong and other places began to flood into Hebei. After the northeast ban was released in the Republic of China, it became a trend in Hebei, Shandong and Henan. Countless poor immigrants who could not survive in the mainland married and had children, and after the founding of New China, they were encouraged to emigrate to the Northeast. So it is not surprising that there are so many people in the northeast now.