Doctrine drives design.
The German army infantry doctrine emphasized the crew served weapons over all other infantry weapons, mainly the machine gun. For example, in the assault, the assault element (say a a squad, but the principle is the same for a platoon or company) would use concealing terrain to mask their approach while the machine guns and mortars of the company and battalion (support element) would provide covering fire, while bounding forward to keep up with the assault's advance. All this time the assault element was NOT to fire their weapons to preserve the element of surprise. When the objective was inside 100 meters from the assault element the assault element's MGs would open fire on the objective and the supporting fire would lift. The assault element MGs would then bound forward under covering fire from each other, only when there was one MG would riflemen provide covering fire. Normally, the rifle was only used inside 100 meters and then only as support for the MG, if there wasn't another MG available. The final assault would be accomplished with the bayonet and grenades. (Note that the riflemen in the support element, don't really do anything, except hump ammunition forward to feed all those MGs.)
For this type doctrine, the simple, easily produced, relatively light, Kar 98k was perfectly adequate. It also explains why a "super-submachine gun" like the MG-43/44 were acceptable, the average rifleman never shot at anything beyond the range for the final assault, preferably less than 100 meters.
US Infantry doctrine was totally different, placing far more emphasis on covering fire from riflemen in the support element, which means the rifleman needed weapons with longer range and better rates of fire.