I know it’s probably an unpopular view, but I’ve found it to be true a lot.
It's not. It's the same reason why Linux is everywhere that isn't specifically consumer oriented and front facing. Even most UIs that are designed to mimic Windows are made by tech nerds like us who just assume the users don't know what they want. But they do, they're used to what they know. That's about it. It doesn't help to say "the Windows UI is garbage anyway", it just needs to work and feel familiar. I'm sure Linux could actually slowly take off if there was significant effort put into making it as straight forward as Windows on the front end but nobody really cares about that.
Does this all matter though? Afaik the browser if fully open source, even the crypto stuff so all the shady stuff would be detected (and has as in your examples). Like all of the issues you linked at this point are years in the past. I don't use Brave personally but it being completely FOSS is a huge plus even if the company itself might be weird. On the other hand you have something like Vivaldi that looks like "the good guys" but you'll always have to trust them as well because they're not fully open source.
I use FF but you just cannot deny that using a Chromium based browser has many security advantages over Gecko, especially on mobile. I takes Mozilla seemingly years and years to implement security features like Chromium. They don't put the necessary priority behind this.