Him being passed over for promotion and the ultra competitiveness along with favoritism are what led to him still being bitter about his native country. Personal ambitions and seeking for personal glory are what's causing this prominent research scientist to seek out and work for a country that seeks to dent/stunt his country's rise. And that's very unfortunate for China because it goes to show that personal ambitions, seeker of fame and fortune will be used by vainglorious Chinese like Chen into betraying their country regardless of outcome.
You know that a lot of Chinese table tennis player play for foreign countries. They are mostly the 2nd tiers in China, or they are the 1st tiers but not the best. But all of them would be 1st tier in other countries. They probably will never have a chance to enter Olympics if they play for China. But they certainly will be able to enter from other countries.
This is ultra competitiveness, but it is no fault of anybody, China has largest population, therefor largest talent pool, largest number of Ph.Ds. Of course some will loose out.
He is not a party member, so going up the ladder in a military institution is certainly difficult if it is possible at all. But if he is so brilliant, why not move to civilian institute.
We shouldn't necessarily believe what he said in the article. Everybody will blame others for their misfortune especially when being desperate like him.
Also, I won't blame him for "betraying". He went to US because there is a open position and the salary was higher than in China (even if he got promoted), his house in US would be multiple times larger than in Beijing or Shanghai, he would be able to have two cars while non in China due to the restrictions on pollution, etc. etc.
This is merely a personal bet on his future and turned out to be a bad bet ruined by Trump's fanatical policy.