Why not? As much as possible, this video says it all and is proven.
Muscle memory works on such a principle that the body does it on an instinctive level, plus when you sit on the bike the instinct of self-preservation is triggered, therefore it turns out to pedal so as not to fall)
It's simple. Because that's how memory works.
There are two types of memory: explicit and implicit. Implicit is marked by the fact that it is almost or completely unconscious, therefore, once you have learned, you no longer need to be aware and imagine how you need to pedal, keep balance, turn, and so on. This is done unconsciously.
An interesting fact: with amnesia a person can train implicit memory and it stores some information. For example, if someone rode a bike, and then caught amnesia, he will not forget how to ride a bike.