Very few companies would be able to manage a gigantic project like Chromium.
I happen to be poking around the Chromium codebase the last few days. The size of the codebase itself is at the same level as all of our company's code. Something as important and critical as GPU rendering is only a small part of the entire project. You also have v8, ChromeOS, ANGLE etc to worry about, all requiring experts in those areas. Not to mention things like Widevine and other proprietary technology surrounding Chrome.
I'm pretty sure they can, and do. The vast majority of Mozillas revenues come from Google for being the default search provider. The fact that Google pays Mozilla, Apple and Samsung (among others) to be the default search provider has been an issue with regulators, but as far as I know there has been no rulings on it (yet?).
It's 95% of an operating system. In a way it is it's own OS. Chromium has ~ 500+ distinct APIs and features such as web APIs, extension APIs, DOM, JavaScript APIs, and platform-specific features.
I happen to be poking around the Chromium codebase the last few days. The size of the codebase itself is at the same level as all of our company's code. Something as important and critical as GPU rendering is only a small part of the entire project. You also have v8, ChromeOS, ANGLE etc to worry about, all requiring experts in those areas. Not to mention things like Widevine and other proprietary technology surrounding Chrome.