Not a Google Employee , but in 99% of the case it's money + experience/situation.
This is similar to what others tech company are doing ( Reddit , Adobe etc.. ) in terms of arbitrage when they decide to enter Chinese Market , Partner with Chinese VC or with ideas that challenge their values.
Regardless of where you'll go in tech you'll end up in Amoral corporations like Google/Amazon/Microsoft which are driven solely by Money and Growth , regardless of the consequences. ( Remember Gillette and Child Labour ? Nestlé ? )
Also , the last people who tried to Unionize at Google , which could have enable them to do something about it , got laid off instantly[0] , same pattern happened in all others tech companies...
[0] https://www.theverge.com/2019/11/25/20983053/google-fires-fo...