Discord was one of Equestria's greatest enemies, so why would Celestia want him released from his stone prison? She said so that he could use his powers for good, but what possible good can come from the Spirit of Chaos? What if Celestia had an ulterior motive for reforming Discord? Something she hoped that Twilight and her friends would never find out. Being a leader for an entire nation comes with many responsibilities that sometimes includes making the hard choices.
This story is about what led to the events of Keep Calm and Flutter On, it is about why Celestia would want to reform Discord.