* The Precursors created the Flood
* The Didact HATES Humanity cause back in the Human-Forerunner war, humanity killed all his children.
* Humanity effectively wiped out the Forerunners in the Human-Forerunner war, by destroying all of the Forerunner data on the flood, including the cure. Probably another reason why the Didact hates humanity.
* However, the Didact regretted annihilating pre-historic humanity, cause he didn't realise that the Flood was the reason behind humanities aggression during the human-flood war (pre-historic, before the mass firing of the Halo arrays)
* Didact is DEFINITELY in the game (which you all know of) cause of his glyph etc.
That's all for now, I may add more later.