I had a sudden thought after watching Afterlives: Ardenweald, and it would not get out of my head.
So I have spent the better part of then until now going over everything I could find to see if I was wrong, and I cannot disprove this, but it makes total sense.
What broke the machine of death? seeing Ursocs death narrows our timeline extremely, to the point where I think there is only one possible cause that lines up.
The Defeat of Helya.
What we know, is that Hellhiem and the Halls of Valor were made almost pocket dimensions. made by Helya herself as a place for the Vykrul souls to go after they die. those deemed worthy went to Odyn. Helya took the unworthy. effectively keeping all those souls, that Anima away from the shadowlands.
Sylvanas makes a deal with Helya, one we do not know the details of, but we know at that point she was working for the Jailer. from what we have seen in beta, the Maw has been effectively staved of any Anima, the reason being to keep the Jailer imprisoned.
Helya is defeated, what happens to all the souls she was keeping in Hellhiem? that energy, that Anima.... goes to the maw, effectively jump starting it, giving it the power to push and gain control. allowing the jailer to empower those working for him to act and put plans into motion.
Thoughts? comments? did I miss something? do you have something else to add?