They're not, technically. They're hegemons, which doesn't make them much better. In fact, I'd argue the situation is worse.
Chrome predominantly owns the web at this point. There are few contenders, and making a new browser is a lot of work (see the Verso browser). Google has the arguably unearned luxury of dictating what APIs and protocols the nebulous "web" should use, can throw a bunch of money at adding them quickly, and leave competitors struggling to keep up, effectively buying chrome's guaranteed superiority.
"But there are standards committees!" Yes, but it really doesn't matter when Chrome either uses its own APIs privately on its sites[0] or just adds new APIs without any committee consideration for people to use and fall in love with and demand that other vendors add them (or something similar, such as proposing a great idea at the committee, it's accepted, and the other vendors lagging for months or even years - see WebGPU as an example).
One might think "it's just a browser". Yes, but browsers are -for better or for worse - the global defacto for sending and receiving almost all of our sensitive data. Even "desktop apps" like Whatsapp, Signal, and Bitwarden all either use or have used Chromium to display their contents (via Electron).
Much of the community has asserted Google owns the web at this point, and I tend to agree. It's very, very hard for smaller vendors to have much of a day these days without Google getting theirs, too.