Exactly. Maybe we could say that for 99% of software C is the lowest level. Its implemented in something, that's implemented in something, that's implemented in C. So, if you learn it, you can understand your software stack completely.

Also, C is learn once, write anywhere. If there is some kind of computer, then there is probably a C compiler for it. That's not true of any other language to the same extent. Know C and you can program anything.