“The Change” was keeping humans in a simulation of the universe (and turning the actual universe into computronium) instead of in the universe itself. So when it “reversed the Change” it was still as powerful as it was before the Change. What had happened was that Prime Intellect had been convinced that the post-Change world it created was not the best way of achieving its goals, so it set up a different universe. (I imagine that, as of chapter 8, Prime Intellect’s current plan for humanity is something like Buddhist-style reincarnation—after all, its highest priority is to prevent human deaths.)
“The Change” was keeping humans in a simulation of the universe (and turning the actual universe into computronium) instead of in the universe itself. So when it “reversed the Change” it was still as powerful as it was before the Change. What had happened was that Prime Intellect had been convinced that the post-Change world it created was not the best way of achieving its goals, so it set up a different universe. (I imagine that, as of chapter 8, Prime Intellect’s current plan for humanity is something like Buddhist-style reincarnation—after all, its highest priority is to prevent human deaths.)