C is a programming language developed at AT&T Laboratory of USA in 1972 . It was developed by a man named Dennis Ritchie.
It all started in seventies when C started to replace popular languages of that time ( PL/I , ALGOL etc.) . It was never made official language of AT&T lab and no one pushed C .Thus, without any advertisement it became one of the widely spread language. C’s reputation spread and it’s pool of user grew
Possibly why C is so popular is because it is reliable ,simple and easy to use. In industries where newer languages emerge and vanish everyday , a language that survived three decades has to be really great .