Legacy Of Cthulhu RPG: Before The End

In a future closer than we imagine, humanity is lost amid conflicts, wars, and diseases in the ceaseless quest for power, bringing disgrace to the whole world. In the end, when it seemed that things could not get any worse, those who had always been waiting revealed themselves in jubilation: Dark Priests and Cultists, scattered all over the world, brought back the Great Old Ones, who completely devastated civilization as we know it. But what happened before the disaster? What facts led the world to this tragedy? Would it be possible to prevent (or at least remedy) such a disgrace?