If all Google engineers left at the same time, Google would still probably end up dominant by hiring new folks to get things back up and running.
No amount of human labor will be able to close that data gap.
In fact, this is already happening. DDG is building its own crawler (I often see the ddg user agent on my web properties) and they don't have any open "machine learning expert" positions.
Now DDG is interesting. Their results are noticeably worse (YMMV). But they are using privacy as the selling point. I wonder if you can possibly have results as good as Google’s, or be as big and profitable as Google, while maintaining user’s privacy. I guess we’ll find out.
IBM was constrained by an antitrust ruling. Which gave Microsoft an opening. Microsoft itself was then subject to a similar action 20 years later. So it's been another 20 years since then, so the time is ripe to clip googles wings.
Railroads begat AT&T begat IBM begat Microsoft begat Google begat Facebook begat Amazon.
What some of us who've seen this rodeo a few times are beginning, slowly and dimly, to realise is that what we'd prefer is a healthy competitive marketplace within, sa, telecoms, chips, operating systems, publishing, search, retail, and the like. Simply crowning an endless succession of new storks as king of the frogs is losing its lustre.