Well clearly they built it so they own it. So if you don’t like it, it’s their way or the highway!
What exactly did they built? AFAIK, even search engines already existed when they entered the game(they just did it better). The fundamental protocols that makes the web work weren't invented by them. What made you think "they built the web"?
They do somewhat control the fundamental elements that make the web work. Blink/V8 is obviously more powerful than Webkit, Gecko, as far as the market is concerned.
If Blink and Google both implement a feature it becomes a defacto web standard.
too bad you cant talk to Berners-lee and the original DARPA crew about this