Long story short, its that members of the Death Cosmology want it to be the Dominant One. So they sent a bunch of infiltrators to stir crap up with the other Cosmological Forces, using their natures against them. They knew Order was the type to really hate the Void Lords consumption, so they settup things to trigger that conflict. With Order, The Light, and (to a lesser degree) Fel all essentially breaking themselves to pieces in their conflicts against Void. We have no idea what Death has been doing with Life.
Its convoluted, but essentially boils down to elements of all the major Cosmologies are in spitting matches with eachother for dominance. Members of the Death Cosmos just used that fact against the others to pit them all against eachother first; to weaken the crap out of most of them before Death made its move. With Denathrius and I guess Zovaal spearheading that ideology. And the rest of the Panthion not agreeing with it.