Where did you get the notion that many Chinese want to immigrate to your shithole country? For example, 80% of Chinese students, including the US, return home. If things are so bad in China and so great in the west then why are they coming back, and why are thousands of scientists fleeing to China from US?

Maybe because by having a headstart of 2 centuries in industrialization and modernization along with pillaging and imperializing most of the globe for the last century , the US has accumulated a ton of riches and a global cultural hegemony that makes citizens even in a rapidly developing nation like China want to go there , especially for richer western-phile ones for whom America might provide a better living. And of course as i said western cultural hegemony and global media dominance make it seem like the American Dream is still a thing and that the grass is greener at the other side. But still your point ,even without this nuance, is losing steam. Chinese migration numbers to the US has been rapidly falling ,as are Chinese enlistments to US collages and schools, with the number of Chinese people repatriating multiplying over the years and the common feeling being "US kinda sucks after all"

For the same reason many Americans dream of Europe, Southern Europeans of Germany, Europeans that move to the States or Switzerland, or even say Central Asians that move to Russia, people in the countryside move to the city, etc.

There's the promise of living richer and having more or simply having it easier. There's nothing else to it and an improvement from Migration doesn't even necessarily have to come true.