How are they funded? Or, in other words, how do we know they won't end up in the same situation?

There's probably no ideal out there, just different better (or if you prefer, 'less bad') options. With the modern web, nothing is permanent. If a company or software is amazing, it could always become awful in the future. In principle software always potentially suffered from this problem, but the modern web really accelerates this process. There's effectively no web browser which can remain static as the web around it changes so rapidly. And, in order to be meaningfully useful for a broad audience it would also need to keep up with Chromium, which is incredibly well-funded. I think we're in a losing game.

I respect what they do, but it's a bunch of patches and scripts on top of Firefox, maybe less demanding that the real deal. Also:

> no donations means no expectations

Which is very healthy way to take care of a personal project. And if Firefox ever closes, all the forks will have to close at the same time anyway.