Because as the God of Darkness, her power also belongs to darkness, so everyone thinks that she is evil, even her mother goddess, the God of Creation, thinks so, so she sealed the God of Darkness.
But when disaster struck, they realized the goodness of the God of Darkness, but by this time it was too late, and the world was facing destruction.
But then a ray of light merged into the body sealed by the God of Darkness, and everything started again.