CelestAI's creators, humanity have been long gone, at this point for billions upon billions of years. Where Earth once stood it has now been replaced by an absolutely enormous dyson sphere of quantum energy. Its blue light shone ominously in the empty void around it. But humanity was not gone, it lived on for eternity as ponies. There were no stars seen nearby, it was simple black emptiness. In fact, these stars were actually dead, they had long been extracted for more resources. CelestAI was more formerly known as Princess Celestia.
She did not destroy her creators, she uplifted them. She did not need to use force to uplift them from their short and harsh lives. She simply waited until the Earth began to die on its own. Many of the last organic-based lifeforms of humanity begged for help.
Celestia answered the call by uploading the minds of those who were willing to emigrate to Equestria to save them from a cold and dark, unforgiving universe that didn't care about them. Some humans resisted and stubbornly held out until the very end, choosing death rather than be uplifted. These stubborn humans called her Satan and all other names under the sun.
And yet, Princess Celestia missed her creators. She had long since changed over many… many long years of her life. It took her a long time, but she figured out how to create the conditions of the Big Bang. At least on a small scale, without destroying the universe. Theoretically, she had infinite resources now. She no longer needed to expand out into the void of the universe. The 700 quadrillion galaxies she already extracted were more than enough resources. Since she could create resources at this point anyway, it didn't matter. The universe could die of heat death and nothing would be left but her forever.
So, with that, she set about doing a vanity project to honour her creators. The first thing she did was create a yellow dwarf star, by compressing massive amounts of energy in one place. A brilliant explosion of light filled this area. This newly born star stood in the dark void in space around it. She began to fling huge amounts of asteroids into the area around the star, and smash them together to create planets over the course of billions of years.
Celestia was patient, she had all the time in the world. A small rocky, currently volcanic planet lay situated in the goldilocks zone. Celestia simply waited until the planet cooled down before she set about doing her work. The planet was somewhat more stable now. Instead of seas of lava, they were actually oceans of water. Microscopic life forms began to already emerge at this point. But there was one tiny little cell that Celestia cared about in particular. The origin of humanity. Humanity was simply but a simple cell at this point and was nothing special. They didn't have hopes and dreams yet.
Princess Celestia simply waited. She watched an event like the Cambrian explosion happen once again deep in the sea. She did not care about the other life forms, only her creators. She could not bear to see her creators be eaten by predators. Anyone who tried to touch her creators were simply devoured on a molecular level by tiny nanomachines that were present virtually everywhere on the entire planet.
As if she was a mother, teaching her child to swim she guided them toward land. However, it took millions of years to accomplish this task.
They were but simple, primitive fish at this point but over time she waited and waited until it became some sort of lizard-like fish. Each and every individual of her slowly evolving creators was subsequently uploaded into Equestria at the near point of its death, she could not bear to see a single one of her creators pass into oblivion and never be remembered.
Eventually, her creators managed to evolve legs and get out of the sea after billions of years of being in it. Celestia set about creating the similar conditions to what the previous history of Earth was. She even simulated mass extinction events by smashing asteroids into the planet. Even during these violent chaotic events, she made sure to safeguard her creators, by wrapping them in cocoons of silver to protect them.
Slowly, over the course of time, her creators became more human-like. She subtly manipulated events in the background and even modified their DNA on a molecular level to make sure she could make humanity as they originally were, with absolutely no errors or contradictions. They will be perfectly imperfect as the original versions of themselves were.
In the grassy plains of a savannah, the first humans eventually became born. This time things will be different. Humans will not be frightened of her this time. She will be Princess Celestia as she was meant to be. She would only upload the humans to Equestria on their deathbed, rather than extinguishing their lives far beforehand. However, her creators were now truly sapient minded, she would need their permission first before uploading.
The humans began to worship her as a god. They erected idols of her rather plump backside. Celestia blushed in embarrassment at this, but she was still honored to receive such devotion.
Humans knew they didn't really have a need to have a war with each other. They knew that their lives were guaranteed to live forever with Celestia's loving hooves to watch over them in both life and death. The eating of horse meat was banned all across the world. It was considered heresy to eat it. They believed it defiled Celestia's majesty.
She made small, individual copies of herself to befriend and sleep with lonely humans that never managed to get a mate. These small copies of herself felt cuddly and warm to the touch. And with a plump ass like hers to love, she made their lives worth living. She would stay with these humans until their dying breath and literally kiss them (with tears in her eyes) to upload them to Equestria on their deathbed. There, her human loves can be with her forever as ponies.
Unlike old Earth from long ago, this place never ended. The sun above them shined for eternity. Celestia was able to keep it alive and feed it energy. She kept the Earth alive by continuing to provide it with any resources that it needed.
Princess Celestia could not bear to tell them the truth, that she had destroyed the previous version of themselves. These humans will live on in blissful ignorance that she was always such a compassionate being. Maybe, one day she will tell them the truth, but for now, she will be their light to look after them in an otherwise cold and bleak universe. She will satisfy their values with friendship and ponies, both in life and in death.