Well, it's an app that users access all their online info through - bank, email, search, work, social - everything. Even an open-source, decentralized, blockchain, grass-fed, organic, extra virgin, written in nothing but HTML, released by W3C itself browser could monetize just ~5% of market share if users are downloading their build (or if its baked into the source), considering how much a browser reveals about its user and to the extent the user can be retargeted for: Ads, marketing, surveillance, analytics.
The biggest opportunity has to be driving search traffic to the major search providers all these browsers partner with.
Could also get acquired by a major browser vendor if you have a better product and people are downloading it more than the major ones, especially if both are based on the same underlying engine. Even Firefox still sucks to this day. I'm using it right now (Waterfox) the product still sucks! I know of some browser vendors acquiring others, especially as mobile took off and it was hard to get it right.
Seems like the opportunity is similar to that of social media but slightly more modern because nobody uses new social media anymore but people are trying out new browsers (and you get richer user/usage data).
How does The Browser Company make money? They're giving their product away for free.
Browsers are complicated. It doesn't inspire confidence that the folks in charge of that complexity can't get their heads around a business model.
(Aside: none of their stated company values have anything to do with the product or engineering [1]. They're all about how people feel.)
[1] https://thebrowser.company/values/