Linux has a ton since every big company basically just pays a dev to do what they want.

This is also exactly why the kernel development process has become fully slopped. Those salaried developers come with strings attached. They conform to and promote their employer's development practices.

On a separate train of thought, while Linux may have a high number of salaried contributors, it is also such an enormous project with so many modules that once you get down to the granular level (e.g. a specific filesystem, or device driver), you will still probably find that there is only a handful of people who intimately understand how it works. Unlike most software which fits somewhere between libc and the end user, a lot of the implementation details are completely absent from the kernel. The kernel implements some kind of protocol, and the hardware it interacts with is more or less of a black box.