Ahh it's you. Been a while hasn't it? We WILL finish this.
Just you wait.
Ive noticed this. Everytime the covenant find some kind of forerunner installation they almost always release some kind of ancient alien evil/threat to the galaxy. They released a flood army from containment on Installation 04 and allowed a proto-gravemind to form. The heretic covies released flood from the forerunner labs they have to have done it no one else who could release them was there. The covenant discovered the flood on installation 05 and despite past experience they decide to tamper with things they arent supposed to and then the flood run wild, take over their ships and escape, unleashing a gravemind into the galaxy and giving them a fleet while they were at it.
And I can bet that this faction of covenant that found the chief in halo 4, will free this new enemy and will be at fault for putting the galaxy in peril once again. So how can an advanced alien alliance be this stupid?