C++ had a whole host of compilers and tooling/IDEs pushed by large private companies (Microsoft, Borland, Intel). I think that somewhat qualifies as institutional backing of another sort.
The initial push for C was that most Unix systems arrived with a C compiler included (there were exceptions ofc, and once the compilers started going pricy there was a lot of volunteers for GCC).
Microsoft and Borland both were companies that made money on selling developer tools (it's been overshadowed by OS and office software for MS, but Microsoft had a lot of business selling compilers etc.) so of course they sold compilers for languages that got popular (and in case of MS, later used the compilers to prop the environment for developers building software for their OSes)
