> When you say "controls" it's like you're saying Google has some kind of monopoly power that makes it hard to switch
No, "controls" means decides the rules and what is happening on that part of the market. Any number that is not 100% automatically implies it's not a perfect monopoly and it's possible to switch, but once you are within the area controlled by Google, it's Google's rules. Including removal any content Google doesn't like for any reason, blocking any action Google doesn't like for any reason, etc. So for 91% of the searches, Google decides what you can and can't see.
Google hasn't leveraged their ownership of the browser to enact censorship (frequently on behalf of most vile dictatorships) yet as far as I know (surveillance is another mater) but it certainly did and is using its control over search, advertising, video hosting, etc. markets to do that.