Originally Posted by MinnMan

In my admittedly anecdotal experience, electrolytes are not the only or even the principle cause, but they are also not inconsequential.

If it were purely electrolyte depletion, or even dehydration, the muscles that cramp wouldn't necessarily be the ones that are most tired - i.e., the legs. So simple muscle fatigue is a factor.
If I'm at a high level of fitness, cramps are less likely, so training/fitness is a factor.
But if I hydrate well in a ride, I will be less likely to cramp. So hydration is a factor.
If I hydrate only with water and don't eat, I will be more likely to cramp than if I use electrolyte drinks and keep on top of my nutrition. So electrolytes and/or nutrients are a factor.

There are times when I also get cramps during rides that aren't in my legs - i.e., my hands. Whether they are also fatigued from gripping the bars or collateral damage from dehydration/depletion is hard to say.

Shorter: There's no single cause or remedy. It's a combination. That is, assuming some other medical effect is not intervening.