This was probably created to solve the challenges associated with mounting an open rotor on a traditional airplane. Open rotors combined with bleeding-edge engine core technology appear to offer very significant fuel efficiency improvements (which in turn makes emissions goals easier to achieve since you burn fewer dinosuars).
An open rotor is too large to fit under the wing, even a high-wing would need to be on stilts and then you have FOD issues. If you mount them on the rear (like the original MD-80 test platform) a fan failure will likely take out the OTHER engine as well as whatever equipment is in the tail bay, and maybe the verticial stab/rudder too.
This design keeps a fan failure from getting the other engine or vertical stab/rudder. You can simply armor the sections of fuselage adjacent to the fans. Not sure about how you keep a failed front fan out of the rear fans though.