Basically, the business model of Brave is that they want to block ads on websites so that the browser itself serves the ads instead.

They aren’t blocking ads for the user’s sake, they’re blocking ads to kill their competition.

Brave isn’t popular enough to actually disrupt the online ad industry like that yet, so they’ve found other ways to make money (like crypto). But the built-in ad network was their original idea. It’s not exactly a pro-user organization.