>>96484401
Do you know who has the same line of thinking as Roboute? Warmaster Abaddon. His ambition is for the Marines to rule over the Imperium that they created. As Horus did, Abaddon sees baseline humans as too weak and unworthy to lead the Imperium. Mortal men ruling, in his reckoning, would only lead the species to ruin. He dreams of an Imperium ruled by Space Marines as it was always meant to be before the lying Emperor betrayed his angels by elevating mere men over them.

So fundamentally, Roboute and Abaddon are in agreement. I think it's part of GW's plan to make the two characters mirror each other.
If both of them want the same thing, couldn't they has things out?