That can only be done if Firefox has users.

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.

Can someone answer why this is wrong instead of just downvoting?

Well, it's wrong, because it can not only be done, if Firefox has users. You don't need to care what 99% of the world population is doing. As long as Firefox exists, you can use it.

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.

But it isn’t – the amount of open source devs working on FF depends on how many people use FF, and the amount of fulltime devs depends on funding, which depends on the amounts Yahoo or Google pay, which depend on how many users Firefox has.

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.

We built Firefox 1.0 and shipped it to the world with zero revenue. Open Source is funny like that. Some people work on it because they love it, not because they're being paid.

Indeed, and one can surely maintain Firefox 1 or 2 easily with a bunch of volunteers.

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.