https://en.wikipedia.org/wiki/Usage_share_of_web_browsers#/m...
IE was stagnating, slow, and extremely vulnerable to malicious behaviors. The net result was that the web became a very hostile place, while Microsoft was pitching various "post web" strategies like WPF. Google had been a big financial supporter of Firefox but not to a degree where they could direct the project or push their own agenda. At the time many viewed Firefox as slow and bloated.
So Google made their own thing, and it worked admirably and we might be in a very different world if they didn't. They dramatically improved the state of the art for JavaScript, added intrinsic hostile activity and site blocking, started dramatically accelerating the adoption of technology improvements (by implementing very early proposals, often to much consternation), etc.
The web was less dangerous. Google's cash cow was protected because there was less of a draw to go to alternative platforms.
That, I think, was their primary intention and it was aligned interests with users. Everyone is happy with the web.
And honestly I do think this ad blocking thing is a bit of "fake news" (e.g. it is being grossly misreported). Google is proposing a solution that offers more privacy from the extension, and it seems very similar to what Safari has done (and which is very widely viewed as a great design).
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