Indeed safe strings in C are hard to do, but the nul termination is not the end-all-be-all of C strings; indeed, there is often a way to specify maximum string

Indeed safe strings in C are hard to do, but the nul termination is not the end-all-be-all of C strings; indeed, there is often a way to specify maximum string length (e.g. %.#s format in the prints family, strncpy). So mmapped strings are actually useful. The bigger problems is embedded nuls, which can’t easily be sidestepped in the C strong framework. Regardless, C won when the world was not yet well connected, and vulnerabilities mattered much less. It might not have won if the match was held today. The wake up calls were the Morris worm (intentional) and the AT&T outage (unintentional, and more of a logic error iirc) but by then it was too late.