There are high level systems languages starting with JOVIAL in 1958 for the SAGE radar system.
C only exists instead of the alternatives, because according to Dennis Ritchie himself it was more fun to create C than using something else, and I quote:
"Although we entertained occasional thoughts about implementing one of the major languages of the time like Fortran, PL/I, or Algol 68, such a project seemed hopelessly large for our resources: much simpler and smaller tools were called for. All these languages influenced our work, but it was more fun to do things on our own."
From https://www.nokia.com/bell-labs/about/dennis-m-ritchie/chist...
That doesn't quite say what you claim. The choice was because the other languages were too large/complicated, not because of fun.
Quote does not support the claim that the only reason C exists was that it more fun