The ceo is a bigoted asshole, Brave is chromium, it was initially funded by Peter Thiel and they're literally just trying to make their own adsense network.
The self-proclaimed privacy focused browser is tracking your browsing and want to serve you personalized ads, and I think they want to use that tracking data for AI training as well, meaning other people can potentially access it.
And lets not forget about their crypto currency that you can earn by turning on special ads. Which they seemingly unironically called it "Basic Attent Tokens"..
TL;DR: The company is basically a sham company trying to usher in a dystopia. Where you'll get paid for staring at ads, while having all your data stolen and sold back to you.