I am speculating but here might be reasons axial flux motors have advantage over radial flux motors:
1) torque: torque = applied force x length of the lever. Because the radial flux rotor must fit inside the stator, therefore radius << motor outside diameter. With the axial flux motor, the rotor is adjacent to the stator, therefore radius < motor outside diameter. Axial rotor radius > radial rotor radius.
2) space efficiency: in a radial flux motor you have 1 rotor, the coils arranged so that one end of the coil's magnetic field is useful to work on the rotor, the other end is not used. In an axial flux motor, (1) pancake rotor at each end of the coils, total (2) rotors, the coils can act on a rotor at each end. There is no free lunch here, to do useful work you still must provide more energy to the coil, but you can get the most from the space.
There must be someone here with a better handle on the electromagnetism, please correct me where I err.
Think of the motor as a barrel and you can decide whether you put the magnets covering the barrel walls or covering the top and bottom, and your goal is to have the most magnet surface. At short barrel lengths, you get more magnet surface if you cover the top and bottom instead of the walls.
The area of the top+bottom is (2 * pi * radius * radius)
The area of the wall is (2 * pi * radius * length)
For them to have equal magnet area, you need length to be equal to the radius, which is bad. That makes your motor really thick. In the axial design, you can make the motor thin and still have the same magnet area as before, so your motor now weighs a lot less.
If you want a visual of how significant this size difference is, this image shows the sizes of the two motor types in relation to each other at equal strength because the axial motor no longer needs any of the barrel length: https://imgur.com/qwe3tuH
1) torque: torque = applied force x length of the lever. Because the radial flux rotor must fit inside the stator, therefore radius << motor outside diameter. With the axial flux motor, the rotor is adjacent to the stator, therefore radius < motor outside diameter. Axial rotor radius > radial rotor radius.
2) space efficiency: in a radial flux motor you have 1 rotor, the coils arranged so that one end of the coil's magnetic field is useful to work on the rotor, the other end is not used. In an axial flux motor, (1) pancake rotor at each end of the coils, total (2) rotors, the coils can act on a rotor at each end. There is no free lunch here, to do useful work you still must provide more energy to the coil, but you can get the most from the space.
There must be someone here with a better handle on the electromagnetism, please correct me where I err.