Propeller vs Impeller, incompressible vs compressible flow, extremely low rotor solidity vs extremely high rotor solidity. Completely different engineering design criteria.
Propellers are rotating wings. the free-air wing tip contributes zero lift to the wing - not some lift, not a little lift, zero lift. On the other hand, the tip of an impeller blade contributes a major portion of the lift. This is because the shroud (or duct, or whatever you want to call it) around the impeller prevents radial flow of the air that then tries to flow tangentially around the blade. To prevent that tangential flow we put another blade very close to our blade - so close that the air has no choice but to flow in the axial direction of the rotor. This "no choice" is called "pressure". We are now working in the compressible regime rather than the incompressible regime of a free-air propeller, and the closeness of the blades is called the "high solidity" of the impeller.
And last but not least, on a bypass turbofan, the diameter of the first stage bypass rotor is bigger than the inside diameter of the intake duct. This helps to smooth the transition from incompressible flow to compressible flow.