I would like to attempt an explanation. It boils down to learning complexity.

> why C is used in lieu of other "better-C" non-managed languages, such as C++, D, Nim, Rust, or Zig

I am a system admin. I do not earn my income writing code and therefore spend at most a few hours a week programming. I've spent about 1000 hours writing C code in my life. About 200 hours of Golang. Years of Posix Shell. Years of Perl 5. I've had a little exposure to Java and C++ and Haskell. I have read a few examples of Rust.

C++ has a higher complexity than C. C++'s syntax is more powerful, it has an additional paradigm (the C++ template system), and if you mix in QT you have one more paradigm (QT preprocessor), it has a very wide ranging standard lib (which data structure do you use for lists? vector, dequeue, ...) augmented by QT and augmented by boost. C++ is huge. There is no way I will learn that in my professional life, I simply do not have enough hours of training left. C++ is not a valid successor to C, because its complexity hinders acquiring the language. Rust suffers the same complexity as C++. I will not have enough hours on my learning schedule to acquire a proficient level of Rust.

Golang is nice for me personally. The book "The Golang programming language" is only double the size of "The C programming language", which makes them comparable in complexity. I get stuff in Golang done faster than in C since I find debugging easier.

I have neither used NIM, nor D, nor Zig. All I can tell you is that C is sexy because the language is small and therefore one can acquire it in a life time -- without being a full time programmer.