Exactly. It's one thing to be an idiot on Twitter, it's another for you to donate money to a cause specifically designed to deny rights to people - a cause that was actually successful for a time. That's something that speaks to a fundamental lack of empathy that I'm not sure he's ever directly addressed.
But in any case, I've heard this argument before, and the timeline doesn't make sense. At the time he resigned, Chrome was very firmly ahead of Firefox, and given his track record with Brave, the idea that Eich would have single-handedly saved Mozilla is also pretty dubious to me.
It seems like a disingenuous and lazy talking point tailor made to blame the demise of Firefox on a culture war politics, when in reality it's the fact that Google was willing to throw much more time and resources at the browser market than a non-profit, unimpeded by the same sort of anti-trust and lack of development that brought Internet Explorer low.