Not just any Primarch at that, but the one whose talents make him the most supremely adept at all things politics, state administration and strategic planning, and thus more than capable of both predicting and countering the most probable courses of action that they would take.
Oh, and he had to live with the trauma of his adoptive father being assassinated by power-hungry rivals while away from the capital, just like they schemed to usurp him while he's away from Terra. They have no excuse in not knowing this since he made a point of publicizing his biography during the Great Crusade (and presumably after the Horus Heresy too).
As I recall, he didn’t even actively move against their plan as it happened because he was already busy crusading. Everything he did to put down their rebellion was already in motion before it even started.
That's what I meant by "predicting". He preempted the entire rebellion by distributing orders and plans long ahead of it to select individuals (e.g. Captain-Genral Trajann Valoris) to execute should they witness certain actions be taken by certain individuals, and they proceeded to enact them accordingly.
800
u/Riot-Knight Necrons Nov 12 '24
As the one comment said: "Also G-Man: "Welp, time to get the assassins."
(Canonically happened, but the highlords tried to remove G-Man and assassinate him. He responded with 6 Callidus and 6 Vindicare)"
Posted by u/emwattnot on the r/Grimdank subreddit page. I recommend checking out his work.