Which is the best explanation for the cleavage of mica into thin layers?

As Mica splits perfectly parallel to its base, it is considered to have perfect basal cleavage.

No other cleavage planes are present in Mica so the flaking occurs readily along the single plane.

A good analogy would be a stack of A4 paper.

The laters are easily peelable in one direction [parallel to the base] as opposed to the other axis [refer to the miller indices].