Disclaimer: I do not work at FAANG. Having said that, if you are sincere in trying to understand, consider the following:
1. Not every tech person agrees with you on the degree of evilness of Google. The set of such people is huge, despite what you read here on HN. Google employees are a mere tiny subset. I wish I could remember the name, but there's a fallacy that goes like this: "If everyone has the same information as I do, then they will have the same conclusion. If they do not, then it's likely they are deluding themselves or are malicious". Consider if you are falling for that fallacy.
(I too fall into that camp - my angst towards Google is not their monopolistic endeavors, but the fact that there hasn't been any good user visible thing from them for years. They're not innovating in that space any more).
2. Most people have to work 30-40 years to retire - even in the tech industry. The companies where you don't are the outliers. And in most non-Google companies, life is very mundane. The company/employee relationship often isn't good. There's always politics, and there are always problem people. Furthermore, if you're fairly smart, the level of incompetence you'll perceive elsewhere is large. I could make a rather large list of annoyances in the life in a typical company. Say you're working in one of those, and now see you have 30+ years to put up with this.
From what I've heard, Google has a lot fewer of these immediate, local problems. Overall, Google treats its people much better. I'm sure they have their own problems, but I suspect they're a much smaller subset than the problems at your average workplace.
The key thing to understand about human nature: Local factors will always play a much bigger role than global ones. In the long run (think decades), working for an employer who treats you better is a big gain. After about a decade at a mediocre company, it's hard to tell yourself that "Yeah the working life sucks, but at least I'm not a monopoly!" for 2-3 more decades.
I'll take myself as an example. I was recently asked if I wanted to interview for a company in an industry that had been my dream since childhood to work in. The work they do is changing the world in a way I advocate (as opposed to serving ads). In the beginning of my career, I would have said "Yes, sign me up!" But now that I've worked for a number of years, I know better and immediately turned them down. Yes, they're doing good for the world. But also yes, the work/life balance sucks, and although the salary is larger than mine, it's not near Google level (i.e. if I move there, I still have to work for decades to retire). The company has a reputation of being abusive to its employees.
Local effects matter more.
Now of course, there are companies out there with good employee satisfaction, and with a lot less pay than Google. I would wager most of their employees do not leave for Google.