At the origin, Brave was supposed to be an adware that replaces the ads of the website with theirs.
Just pick your poison but all browser developers need money to live.
The only way to be sure a browser works in your best interest would be if you accept to pay, and nobody wants to do that.
See what has happened with Neeva.
The main reason I moved to Brave is Firefox's bizarre updating model on Ubuntu which causes it to randomly shutdown all the time. Plus on Android, brave just blocks a ton off ads, that firefox doesn't without extensions and fiddling about.
From my perspective it seems that the current FF CEO basically did a hostile takeover of Firefox, that involved maximising their personal wages. Firefox is absolutely for profit, the $millions the CEO takes is ridiculous. I read that they got a personal stipend from Google too, but I've not been able to confirm that. Maybe you're confusing them with the Mozilla Foundation. The way they structure things so you can't donate to engineering on Firefox is skeevy, far worse than a system designed to enable content owners to get paid.
I was a supporter/promoter of FF for 18 years, fwiw.