The rendering engine portion of the whole Firefox vs Chrome debate gets way more attention than it should. It’s really not that important. Someone could fork any piece of the chromium project and have an “independent rendering engine/browser” without all the problems gecko has from a decade of little market share and under investment. Google nor Mozilla make money from their rendering engines as is evidenced by their ability to make money on iOS.
Also, the rendering engine isn’t the way Google is being anticompetitive or violating users privacy, just like no one is really that worried that Google, Facebook, and MS are some of the largest contributors to the Linux kernel. People use a chromium based browser because chromium is better. Google gets people to use Chrome, and gets their data through the code they add on top. Overall though, Google has not been a bad steward of Blink.
Weirdly enough, Blink is the first time we have the equivalent of a shared "OS API", that's due to the browser becoming the main way to run apps (desktop at least) and that is supported by most consumer computing devices
Also, the rendering engine isn’t the way Google is being anticompetitive or violating users privacy, just like no one is really that worried that Google, Facebook, and MS are some of the largest contributors to the Linux kernel. People use a chromium based browser because chromium is better. Google gets people to use Chrome, and gets their data through the code they add on top. Overall though, Google has not been a bad steward of Blink.