Mozilla was doomed from the start.

Netscape Inc. wanted to sell browsers eventually, which makes sense. It's product which requires a massive amount of engineering effort. But, when Microsoft started tying IE to Windows and giving it away free, there was no way that Netscape could actually make any sales. The bigger reason their business was crushed was that Microsoft was also giving away their web server (IIS) away for free, while Netscape was charging for theirs.

Some kids today are too young to know that Microsoft was sued by the US government over this and lost the case (along with what was very likely Microsoft falsifying evidence). But, then Bush Jr. took office and the government basically took a case they had won and effectively threw out the win.

When it was clear that Netscape was going to fail as a business they open-sourced the browser either as an act of charity or spite. The problem is that it's still a massive and expensive project to build a web browser. That's especially true in a world where standards keep evolving and the browser has to keep having new features added.

Since making a browser was so expensive, they needed financial support, and eventually that came from Google. At first Google just wanted Firefox to exist as a hedge so that Microsoft wouldn't dominate the browser market. But, once Google came out with Chrome it was both a way to keep directing traffic to Google search, and a way to pretend they don't have a monopoly on browsers.

But, if 90% of the funding of your project comes from Google, there are some obvious lines you can't cross. So, Mozilla has to keep doing this dance where they make a browser that competes with Chrome, but one that doesn't cross certain lines that would make Google mad and result in them shutting off the funding.

Google would shut off the funding to Firefox in a heartbeat if they took ad blocking and privacy too seriously. But, Google doesn't care too much if Mozilla messes around with AI or ads.