alt Hacker NewsCorrect me if I am wrong, but C is the “greatest common denominator” for several decades already. Java, .NET, go, Rust are very much ecosystems-in-themselves. From the practical standpoint, they can not use each other’s code, but they all can use C libs.
Technically it's only the C API that's important, the implementation behind the C API can be written in any language. The downside is though that you still need a language toolchains X, Y, Z to compile the implementations. Transpiling everything to C removes that one dimension from the build process.