My guess is because Brave is a relatively known Chromium browser that’s been degoogled. Along with built in ad and tracker blocking, and it’s an easy less evil of the two.
I want to like Firefox, both as normal user and as web developer, but something about it keeps bugging me. The UI feels sluggish, sites seem to be slightly less performant, and I can’t seem to get used to it.
That said, I’ve started using Vivaldi, and while it can be considered bloated, I really like the tab options it has, while also offering a degoogled chromium that’s being kept to date.
For me, the difference is how they go about doing it. The tracking Microsoft does is baked into the OS you use, for the sake of… well, not for seeing if people in your friends list also use Word or Teams.
Valve tracks a lot of data too, but also seems transparent about it. They show usercount, active players, it shows up for your Steam friends (if you want). And at the end of the day, they don’t need to appeal to some shareholders. To me it feels like they track for the sake of their products, not for the sake of selling this data.
That said, I do think I’m pretty biased towards Valve in this, so I’m not sure how fair my view on it is