At the kernel level you’re not going to be using package managers, or anything with a GC (rip D)

I don’t think C is particularly good, but it’s “good enough”, and nothing obviously better at these use cases has come along to displace it. It’s been around long enough that it “just is” the tool of choice for stuff for people.

Which of course leads to things like the Linux situation where it’s big enough that nobody actually understands how it all works or fits together.