1. The FBI has been ruthlessly persecuting Chinese people with absolutely absurd charges. For example, "In a grant application you didn't list that you had met for coffee with X other student from your alma mater when you visited China for Lunar New Year. This constitutes fraud and possibly espionage." A grant application is not an SSBI application! These are genuinely absurd standards to be applying to people. The fact that the FBI has been overwhelmingly losing these racially motivated cases is cold comfort - having extremely powerful secretive police harassing you and your family is extremely distressing even if their case against you is ultimately unsuccessful, and the fact that they know they're losing and keep doing it suggests their intent is to try and discourage you from talking to any of your friends or family back in China, or leave the country. Careful what you wish for.

2. Declared academic collaboration between academic institutions in the US and China is being cracked down on as well. People and their families are being investigated with no evidence given as to why, the federal government is contacting US universities and convincing them to end collaborative programs, etc. The reasons given, if any, are that the Chinese are stealing American technology through these academic collaborations. Thinking for two seconds about what, exactly, an academic collaboration is intended to accomplish should show how absurd the "stealing" idea is.

3. A lot of the most valuable work in academia is collaborative, and a lot of the specific career value in being a Chinese national or having Chinese family ties in US academia is that you can function as an expert go-between for the two largest and most important countries for scientific research. When the US is not just devaluing but actively stigmatising some of your skills, it can force people to choose. The US is richer per capita, has more freedoms in many respects, etc, but the persecution by police is going to impact your assessment of where you'd rather live, especially when the PRC has open arms, lots of grant money, and scientists have a good position in society there too.

4. Hate crimes against Chinese people have been increasing dramatically for years. Chinese communities know this and also see very clearly that it's not a priority for either political party to do anything about it. Not much to say about this, it's obvious why you wouldn't want to live somewhere where there are enough people in the population committing hate crimes against you that most people are in community with a victim, and then there's no political will to do anything about it.

4. There's genuine concern about the possibility of war. If you know anyone in the American military, you know that war with China is on everyone's mind. Different dates get floated, from 2030 to 2027 to 2025, but it's essentially received wisdom in the US military that there is going to be a war in the westpac theatre at some point. This view ("We should be prepared") is also essentially bipartisan in the political realm, and American media are doing their part too. Chinese people notice, they can see the current (illegal, racist) persecution by the government, and most of them have enough historical knowledge to understand that the dynamics that lead to the Japanese internment camps haven't fundamentally changed - the camps themselves weren't even ruled to be illegal until 2018, only 5 years ago! If you were Chinese, would you want to stay in America and take the risk that you might end up confined to a camp, or wearing an ankle bracelet with a microphone everywhere just so the government can say that they didn't put a particular ethnic minority in literal camps? Genuinely, would you take that risk, with what you know about America? If the American government goes to war with China, and they decided on this sort of large scale persecution of Chinese people, do you think that any significant quantity of Americans with any political power would stand up for the Chinese people in America, or would it be like 9/11 where the government persecuted Muslims en masse and there was zero political will to stop them for years?