Forerunners, beings who filled the galaxy with life thousands of years ago, were declared an ancient and highly advanced species by the Human race. While the covenant declared them gods, in logical terms the real gods would have to be the Precursors, they were the ones that created the forerunners after all. Although nobody, except the forerunners know this, and many of them believe them to be extinct, ever since the Forerunner-Precursor War, a few of them were spared for times of extreme need. Unfortunately that time of need happened to involve the outbreak with the Flood, and the only possible way to stop them was to destroy all sentient life in the galaxy, which would mean the end of their rule and protection over the galaxy. The possibility of the Ur-Didact being right about humanity was a thing that was fearful to imagine, especially since they won't be around anymore, so a plan was created to ensure all of life was protected and cared for while suppressing the human threat, if ever such event came to be. All in all this plan was created to keep everything in check, except there had to be some sort of event to set this plan into motion, yet they didn't mind it could take a few years maybe hundreds, but eventually the event will happen and it will trigger it. It will trigger The Plan. The Final Solution.