If C mapped to "hardware" so well then OpenCL, CUDA C/C++, SYCL, ispc, etc wouldn't be necessary. The rising importance of accelerators is a big issue for the future of C.
Those languages maps to GPU's, C maps to CPU's. Those are on the same level as C, they aren't the real instructions that GPU's run but they are a pretty good abstraction for GPU instructions.
ispc is explicitly designed to take advantage of SIMD on CPUs and GPUs, its existence is directly related to the shortcomings of C in this area. Likewise, SYCL exists to target accelerators because C isn't even close to supporting heterogeneous hardware or programming. In any case, C does not map well to a massive amount of hardware running in production right now.
A CPU can run any program written for a GPU, yes. But the languages you talk about are no closer to how a CPU work than C is, they might be more ergonomic if you want to take advantage of SIMD instructions but they don't do anything you can't do in C and there are a lot of things you can't do in them since GPU's are much more limited than CPU's.
