Uh, C is not really small nowadays. ISO C specification is about 200 pages long even without all the library. (It's hard to compare directly, but Go is probably around 50~100 pages long when formatted similarly.) C could have been small enough, but ISO C is not.
Also, most of what? Besides OSs, tiny tools, DBs and embedded, C is not used all that much. Where truly high performance is required, the de facto language of choice is C++ (see e.g. browsers) and business applications (which are the most numerous) are definitely not written in C in most cases.
