This I think is a general issue, not particular to Brave Browser. I experienced it just now, so I stated my Chrome browser and immediately noticed the same issue there.
The fact is my mac is running slow right now (very slow) and the reason for the renderer or helper is to kick in and render the page, it is some kind of mechanism. The real issue is, the computer being slow, which could be it is busy doing something or updating index, I am attaching my screenshot it. I will probably leave the laptop running for the night and hopefully all the updates should be done the next day.