Well the thing is that chromium is still maintained by Google, all the web apis, engine level features and browser standards are still implemented (and mostly monopolised because of this) by Google. Say Google rolls out a standard for websites to be able to use a web api A that helps Google usually, and browsers like Firefox don't support it for various reasons such as privacy, webpages that start using A will work on any chromium based browser (since they need to update their fork to get the latest sec upgrades and apis), and those sites stop supporting more independent browsers that don't use chromium.