Can we just state the obvious? Chinese AI peeps left because they want to go back to China. This isn't an unusual trend, as an Chinese American, all of my cousins who came to study here abroad in US have plans to go back to China, unlike my parents' generation who came here for a PhD and stayed.
And even amongst my parents' generation, my uncles who have gotten PhD and tenure at US universities and left for universities in China. The reason being that they can get paid for just as much as in US, for lower living cost, a more compatible culture and in Beijing or Shanghai for better standards of living (yes before the critics jump in with air pollution, human rights issue etc., a good US wage in China could afford you a full-time personal assistant and/or nanny to do your laundry, take care of your kids, clean and cook good Chinese food and you can live in a nicer part of the city with better infrastructure than most of US lol; and you could still come out with lower cost of living).
Isn't Andrew Ng working in Silicon Valley? It is difficult to recruit in Beijing these days given the air quality, cost of living isn't low but not that bad either.
I assume you're referring to Andrew Ng himself here, but you don't seem to know him well enough to infer that he wants to live in China -- even though this position does not entail doing that anyway!
He was born in the UK, educated in Singapore, then at CMU, and then at MIT and Berkeley. There's more, but the point is: you're projecting.
AFAIK, most people who choose to work in China are finance professionals, not programmers. But I wouldn't be surprised even if they are programmers. Many companies in China are expanding westward (.e.g Biadu). Bilingual is a big bonus because you can communicate with your co-workers from both East and West. Some people like me can read, write, listen and speak perfect Chinese (Mandarin and Cantonese) and is perfect candidate to work in China.
If we put health issue aside, China's living standard isn't exactly that low, housing price is crazy... and you are a foreginer, you won't go to public school. You will go to international schools and they aren't cheap. But if they earn the same wage as they do back in US, like at least 100k a year? sure, maybe.
Otherwise, I think one of the tedious part of living in China is applying licenses and IDs. According to a research [1], a Chinese citizen may need to apply between 74 to 103 different kinds of ID, license and certificate in one life time.
And even amongst my parents' generation, my uncles who have gotten PhD and tenure at US universities and left for universities in China. The reason being that they can get paid for just as much as in US, for lower living cost, a more compatible culture and in Beijing or Shanghai for better standards of living (yes before the critics jump in with air pollution, human rights issue etc., a good US wage in China could afford you a full-time personal assistant and/or nanny to do your laundry, take care of your kids, clean and cook good Chinese food and you can live in a nicer part of the city with better infrastructure than most of US lol; and you could still come out with lower cost of living).