Whichever private firm wanted that business and bought it at the USPS auction. You are aware that FedEx et al. deliver to rural addresses, right?
Are you not aware that the USPS delivers packages for FedEx on a lot of rural routes? And if you send air, there are rural addresses that FedEx won’t deliver to.
Those people just won’t get service? They dont need mail? Who would bid on a money losing route?