This established a geometric description of the entire category of representations of the Lie algebra, by "spreading out" representations as geometric objects living on the flag variety. These geometric objects naturally have an intrinsic notion of parallel transport: they are D-modules.
Establishing this allowed for a geometric representation of all Lie algebra representations, where each representation is visualized as a geometric object situated on the flag variety. These geometric objects inherently have a notion of parallel transport: they are D-modules.