Default settings are fairly lucrative - the reason why Bing and Edge are somehow viable search engines and browsers is purely because Microsoft ships them as default on Windows. Depending on who you ask, Firefox is either the same or double the browser marketshare of Edge, so that default search setting is still lucrative, if only so that Bing, Yahoo, or DuckDuckGo don't get any of that default search traffic.

Also, while lots of people gripe about Google adtech, they aren't angry about it enough to switch search engines. The company still has the best search in the business, specifically because they have a detailed profile on you. Furthermore, they're still moderately trustworthy by tech company standards. At least for me, I'd rather trust Google or Microsoft than, say, Facebook. My biggest concern with any new Google service is less "will I lose control of my data" and more "will this service stay live for longer than a year or two".

> Presumably many/most of those users are not happy with Google/Chrome/advertising/tracking.

I wouldn't bet on that. A lot of non-tech-savvy people use Firefox because it was recommended by their nerdy friends.

If funding Mozilla resulted in no return, Google would have realized it by now. They have been doing it for quite a long time.

> If funding Mozilla resulted in no return, Google would have realized it by now. They have been doing it for quite a long time.

Conspiracy theory: the return on investment is that the active development of Firefox defends Google against anti-trust accusations.

Is it really a conspiracy theory? It's almost certainly a significant portion of the equation.

You are not alone in this conspiracy theory. A significant portion of Google’s business right now is to fend of anti-trust accusations.