It's about alignment of interests. They believe that there is a business that is valuable selling a user-centric browser. A user-centric browser does not exist today.
Google Chrome is a frog-boiling exercise where they slowly take away freedoms to run, for example, ad-blocking in the browser and they do so under the name of security. They've already tried to push the web integrity initiative. They'll try again.
Mozilla, as I've already pointed out, is criminally mismanaged in the sense of poor allocation of resources towards building a better browser. On top of this, they have brought in a number of executives from Meta that have made a number of changes that erode the privacy of Firefox users. They can't ship any features that are hostile to Google directly because Google is their primary source of funding.
Safari is written by a company that has no vested interest in seeing the web be good enough to replace native apps because that company makes gobs of money being a middleman selling native apps.
Vivaldi is closed source.
LibreWolf, IronFox, WaterFox, Icecat, Cromite, Ungoogled Chromium are all similar in that they are drafting the work of the multinational corporations, but ultimately are volunteer efforts that are sustainable only as long as the volunteers continue to donate their time.
Brave is essentially trying to create a business doing what those privacy-focused browsers are doing. The challenge is they somehow need to monetize without compromising privacy, which has been a continual challenge for every browser manufacturer.
Again, I'm going to say it for the third time in this thread: the version of Brave that I use doesn't collect telemetry or serve ads because I paid for it. I can verify its behavior because it's also open source. Not a single person has responded to this very simple fact.