Riemann was a mathematician who lived in the 1800's. As far as I know, he had no interest in physics. Before his monumental contributions to the field of geometry, we didn't really know how to visualize a curved space from within the space itself. For instance, we visualized a two dimensional sphere by picturing that sphere embedded (sitting within) in a larger three-dimensional space. Curvature, for instance, of the two-dimensional sphere was merely curvature with respect to the larger three-dimensional embedding space.

Riemann showed how to consider the geometry of a manifold "intrinsically," (from within) in terms of a tensor, called the "metric tensor." It was no longer necessary to think in terms of an embedding space. What a tool he had devised. I doubt that he ever, in his wildest imagination, thought that physicists would eventually picture the universe as a four-dimensional spacetime incorporating his metric tensor. It is a good example of progress building upon a foundation of previous contributions.