As a browser vendor, yes, you have to try to not piss off advertisers, because if website owners don't make money off of your browser, they're not going to test against it much, but why would you list that reason specifically for Firefox?
Firefox is the browser that's willing to bite advertisers' hands more than any other browser. They even ship effectively an ad blocker in Private Browsing.
Blocking a few egregious ad types is not at all the same as the blocking of privacy-invading cookies as Apple is doing.
> The Chrome ad blocker doesn’t just help publishers, it also helps Google maintain its dominance. And it advantages Google’s own ad units, which, it’s safe to say, will not be in violation of the bad ad rules.
Right, but it's a start - meaning they might eventually get there. It means there is pressure and that they may be obligated to take notice. It's not the end, it is the beginning.
Microsoft might, even though Bing is profitable and in 2015 brought in ~ $1b a quarter https://techcrunch.com/2015/10/22/bing-is-profitable/ . Might be too much money for Microsoft to ruin it.
All Apple right I think, but if they wanted to hurt Google they could start a search engine, maybe by buying DDG.