No, many left within 2 years.

The average for Google is 3.2 years. For most, that is not FU money.

Just long enough to open the doors of any other job interview and bail to a company that doesn't shuffle them and their team around the office like game pieces in a never-ending re-org, a company that makes actual products instead of surveillance advertising systems (as the latter is impossible without the former), or a company that makes decisions not to work with oppressive governments based on more factors than if it will earn more than the potential PR damage will cost.

So, approx. 3 years == disillusioned?

Unless it was a planned stepping-stone all along, to land the real "dream" job and have the credentials to command a more magnanimous compensation than they would without that Google tenure.

For 'beginners' they usually don't have the experience or the network to plan such a stepping stone ahead of time.

If you come in the side door (shift sectors, side-learn upgrade your capabilities) you may have the experience to plan ahead like that. But this was about beginners so I suppose that doesn't matter in this case.