OK, I guess I do not know enough to guess why that happened. Usually the opposite happens, where the sides bulge because of the weight of the cheese causing the whole to collapse slightly.
But aside from that, that cheese looks very good. You have an excellent rind, which is not an easy thing to master. Even if you don't have an emmentaler, you have a good cheese! I would bet you have something close to a real Swiss style gruyere with a very mild PS flavor.