Chromium is in such position that their implementation of new elements and APIs set the de-facto standard for the Web and Safari and Firefox have to follow suit.
This overpowers the governing body (W3C), where they have to accept it and pretend they remain relevant.
A bit of history: When Internet Explorer was the dominant browser of the Internet, other browsers existed and their usage was in healthy proportion, among each other. People could choose whatever browser they wanted and be sure its browser engine was independent.
When Chromium/Chrome came in 2008, it changed the game to what we have today: 85% Chromium-based browsers, 8%-10% Safari/WebKit and 2%-3% Gecko-based browsers (Firefox)
Whatever Chromium does, others have to follow suit. The bulk of the userbase is there (unfortunately). No real choice exists for a governing body to effectively apply standards.