C was already implemented on several quite different machines and OSs, Unix was already being distributed on the PDP-11, but the portability of the whole system was new
The number of UNIX installations has grown to 10, with more expected...
Pretty much everything on the web uses those two things: C and UNIX,
It seems certain that much of the success of Unix follows from the readability, modifiability, and portability of its software.
Likewise, C managed to escape its original close ties with Unix as a useful tool for writing applications in different environments.