OKAY. Maybe this is reaching. Danuser already said that this reaches all the way back to ICC. What if she saw made a deal with the Jailer in the Maw then, but couldn't fulfill it till Legion. She knew she needed to gain leadership to fulfill her plan. She got the lantern from Helya to capture Eyir, and then Genn smashed it. What if Helya told her that smashing that would cause problems with Death which also benefits Helya. She baited Genn to follow her thinking he was doing the right thing, and after that happened, death itself broke. From that point, her only plan was to cause as much death as possible which is why she burned Teldressil, and kept causing big scale death around her. All the death helped her continue to get overpowered to the point she could kick Bolvar's ass and open up the Shadowlands. At least that makes sense to me.