Why couldn't coraline see the mouse circus that the man with the big moustache train?

Coraline couldn't see the mouse circus that the man with the big moustache trained because it was part of the Other World, where reality is distorted and controlled by the Other Mother. The circus was a creation meant to entertain and distract her, but it was hidden from her in a way that only the Other World could manipulate. As a result, Coraline's perception was limited, and she could not fully experience or understand what was happening around her.