The basic idea is that cadence is a result of the important factors of power, torque, and the rotational intertia (I am not a physicist, that may not be the exact proper term).

People often say low cadence is bad for your knees, but it's really that high pedal force (torque) without building up the supporting/stabilizing muscles, liagments, tendons, etc. is the problem.

A low cadence, by itself, is not necessarily a bad thing. If I am just cruising at a nice easy conversational pace, for example, I will be riding at a low power and low cadence. If I am riding tempo, I will be riding at a higher cadence and moderate power. And if I am riding hard, I will be riding a high cadence and high power. In those situations, my pedal force will all be fairly similar.

The bottom line is that I have a comfortable torque range and the cadence falls where it needs to to get me in that range for whatever my power output is at the moment.