I presume it was because prior to my comment, no one had yet explained to the guy that you don't need to deal with such a proxy setup to block ads in browsers.
So, your comment sort of made it sound like ad blocking not being too great for him, was because of Firefox and that Brave would be better at it, whereas it really just was because of a missunderstanding of the guy.
Besides that, Brave is also controversial. As much as some people have screamed bloody murder, because Eich's free speech was supposedly taken away by journalists/SJWs/Mozilla or whoever, a good other percentage of people do think that his donation was wrong and that he should have reflected on it and distanced himself from this (past) opinion.
Furthermore, many people think him basing it on Chromium was wrong. No matter how pissed off he might've been at Camp Mozilla, and no matter how much journalists would've slandered him again, if he started supposedly trying to work with Mozilla again by starting a fork of Firefox, there's just no way that you can work for 17 years on anything and then a few months later go "Actually, this competing product is better".
Chromium being Google software and him trying to sell his Chromium-based browser as privacy-friendly does not help it either. There's millions of lines of code in there with tens of thousands of design decisions, all made by the biggest data broker on the planet. You're not patching all of those out in any reasonable time frame.