Once you begin to understand these things, you can see how Ruin was trapped even though Preservation’s mind was gone, expended to create the prison. Though Preservation’s consciousness was mostly wiped out, his spirit and body were still in force. And as an opposite force of Ruin, these could still prevent Ruin from destroying. Or at least keep him from destroying things too quickly. Once his mind was freed from its prison, the destruction accelerated rapidly.
