Using the example of a hub mounted on an axis and attached to that hub were a series of weights attached to arms that were attached to the hub with horizontal hinges. This means that the weight on the arm is free to “flap” but not “lead / lag”.
Now, spin the shaft until the weights are extended outward at a speed sufficient to create “gyroscopic rigidity”. If you had some means of perturbing the individual weights and arms you would experience precession and the weights would move downward on one side of the disc and upward on the opposite side of the disc. If the spinning shaft is rigid and can’t be displaced as a part of the “gyroscopic rotor” the arms and weights would eventually come back to their original position which is extended outward radially from the hub. Now, in this example there is no swashplate, which would keep the arms, and weights in the commanded position and that is why the arms and weights would return to the radial position.
Now lets talk about the CH-53, which has a lot of blades just like the example above has a lot of weights and arms. It also has a swashplate and the helicopter is a free body in space. If you perturb the blades via the swashplate then the blades will move to the commanded position (gyroscopic or aerodynamic precession) and because of the high level of interlock between the blades and the head (centripetal or, centrifugal force) the head will align itself with the blades. The example above could not do that because the shaft although capable of spinning could not be displaced from its' position.