Which is hard to do when Google competes unfairly, even illegally – which they did, for example with using AdSense for Chrome ads everywhere, and not paying website owners where the ads were displayed the normal rates, or by adding fraudulent banners "Your browser (Firefox) is outdated, upgrade to Chrome now" to Google Search.

You could say that without many users, there won't enough real-world exposure, but at the same time, Firefox will also be targeted far less, so you wouldn't have to worry about security vulnerabilities as much.

And while yes, if at some point Chrome becomes Internet Explorer 2.0 and webpages target nothing else anymore, that could cause Firefox to be hardly usable, but that's then an entirely different nightmare and not anymore relevant to the current situation.

With no devs, you can’t implement those features or the security easily.

And especially for security you’ll want fulltime employees.

Also, you’ll have to pay more than Google pays their Chrome devs to ensure the people will keep working for you.

But maintaining a whole OS with a whole virtualization layer, a whole sandbox system, several supported scripting systems, its own scheduler, its own graphics stack, and support for compatibility with any bug a competing system has?

Modern browser are reaching complexities we’ve only seen in whole operating systems before. You don’t see a bunch of volunteers maintain everything from Linux to KDE at once, it’s hundredthousands of people working in a very different way.

To be able to compete against Google, be able to force them to implement features you pioneer, and force them to avoid implementing other features, to be able to keep up with them and reach better security than them, the current Firefox team is not enough.

Chromium is open source, Chrome is open core. Chromium may also be cathedral (rather thean bazaar) development model, but that's only distantly related to open source or not (bazaar is facilitated by open source, but not required for it.)

Google even openly discourages forks, or any contribution that doesn’t fit their ideals.

It’s only truly open if development is controlled by a democratic community, or if it’s easily possible to be forked and competed with.

Which isn’t the case.

And for users open development is a lot more important than open source: Being able to get their own changes into the browser, ensuring the browser is made by the users, for the users.

Google may discourage forks, but there's nothing they can do to prevent one, and forking Chromium is no more difficult than forking any other project its size.

... or any contribution that doesn’t fit their ideals.

That's one of an OSS project maintainer's more important jobs. I used to maintain some decent-sized open source projects, and part of my job was to say "no" when someone wanted to add something I didn't think belonged (for whatever reason).

Forking Chrome would be like fighting against Embrace, Extend, Extinguish after you’ve already lost (which we have with Chrome, compared to what KHTML used to be like)

Regardless, though, there's nothing that says the hypothetical developers of a Chromium fork couldn't devote some time to merging reasonable fixes & new features from upstream.