I'm not a Fortran or C programmer (so take this with a grain of salt), but as I understand it, Fortran is so optimizable because it's arrays are not fundamentally just a memory layout with pointer math. In Fortran, arrays are abstract entities, which allows the compiler to lay them out in the best possible way to take advantage of vectorization for the current code. Originally, pointers weren't even a feature of the language, though they were bolted on in a later version.

Sure, an expert programmer can replicate this speed in C by being careful about memory layouts, etc. But in Fortran, everyone gets it for free.