>>95816522 (OP)I can't believe they just let other writers fuck it up after Abnett set up a conflict that made so much sense in Horus Rising.
The Space Marines are a kind of class. If you try and make a class obselete, handing all their power and the powers of their leaders to others, sidelining them, you can get a rebellion. Try and get rid of the Samurai you get the Satsuma rebellion. That's all it had to be. Suspicion they were going to go the way of the Thunder warriors.
Even Lorgar's religiousness and the censure he received could tie into this, as well as Magnus' behaviour, not just the dangerous magic, but the general research and scholarly activity. Two Primarchs who tried to be more than generals, not just in the sense of being a good administrator like Guilliman, because that can be read as making society more orderly and efficient so as to better support a war effort. A Primarch who wanted to promote and explore the spiritual, a primarch who wanted to learn pursue knowledge. Primarchs who aspire to realms of human life and experience beyond war. Two defective abberations not doing what they were supposed to do, after which they would be obsolete and potentially even a threat to what they were supposed to build. The way the Emperor comes down on these two puts them on the path to rebellion as they run head first into the reality that they're tools and that's how they're expected to behave, while seeing this from the outside contributes to Horus coming to the same conclusion, all reinforcing the same underlying themes and dynamics.
No instead Horus believes a vision that not only would any moron know not the believe, but which he himself says he shouldn't believe.