FORTRAN is faster for many tasks, and is probably more popular in high performance computing.

Also tasks that can be moved to the GPU go a lot faster. You can interact with those programs in C, but not natively. But some languages, like Julia, can easily move calculations to/from the GPU. And also can transparently take advantage of parallelism.

Julia is in the process of growing rapidly for high performance computing. I don't know if it has officially passed C there. But if not yet, it will.