Pushing for whatever feature they fashion, pushing against stuff that they didn't create, doing things differently for no reason, making sure their software works badly on competitor platforms...
What Google is doing isn't much different from the MS from the 90's, except that they didn't stop improving their browser. At least yet.
Google had long list of oopsies where Google services stopped working because of user agent rejecting non-Chrome browsers.
What does it have to do with the number of people forking and developing their own browser? Agent string sibstitution/emulation has been a thing since time immemorial.
You make your own browsers and issue correct UA (User Agent) only for GMail to stop working. But works fine when issuing Chrome UA. I guess Google is staffed by Howler monkeys, or malicious.