Originally Posted by Over Two Meters Tall!
MEQinc, questioning Guillaumin's loyalty is somewhat spurrious given the circumstances... the Astronomican goes out, no one can get in touch with the Emperor, he knows at least two chapters (WB and WEs) are in open rebellion and actively trying to destroy him, and no other seeming loyalist chapter is doing anything more. Given the circumstances, he was doing exactly what his father would want him to do, carry on the Imperium in any way he could.
And yet, placed in the same (or far worse) situation not a single one of his brothers makes that decision. Guilliman alone
abandons the Imperium in favour of his own empire (not even the Traitors do this). Guilliman sits down, takes stock and says "Screw you guys, I'm going home". And worse than that, he tries to get his brothers to do the same. He tricks Sanguinious into diverting to his position and tries to convince him to stay. Sanguinious has lost much of his Legion, he's been physically beaten in a way he never thought possible, he's far from home and just as confused as Guilliman (if not more so), but even still he recognizes that his duty
is to go to Terra and fight for the Imperium, to die for it if necessary. Other Primarchs repeatedly show themselves to be willing to take risks and make sacrifices (even the greatest sacrifice possible) in order to defend the Emperor and the Imperium. When the cards are down, Guilliman shows himself unwilling to do so. Maybe you can overlook that or think that it wouldn't matter if he was Warmaster but personally I would never, ever chose someone to be in a position of absolute responsibility if I knew
they would abandon it if pressed hard enough.
Regarding the charisma factor among the Primarchs, its obvious from all the HH books describing the pre-Heresy Primarchs relationships that Horus's charisma didn't slake the competitive nature of his brothers, regardless of their personal relationships with him.
Actually I recall the opposite. I recall Horus going out of his way to meet with various Primarchs, discuss their concerns with his new position and address those concerns.
Alpharius/Omegon still chart their own course despite their history with Horus; [snip] Sanguinius, Russ, Kahn, Corax, Manus, and Vulkan seem to be in full kicking-ass-taking-names mode before the Heresy; Fulgrim, Dorn, the Lion, and Perturabo are all otherwise primadonnas who think it should be them no matter who's selected; Magnus and Lorgar will both do their same thing - Magnus trying to stop the Warmaster being corrupted and Lorgar trying to corrupt him... they're both on their same headtrip for enlightenment.
All these things continue because
Horus takes over. Would they still have happened if someone else was in charge? I don't think they would've.
Perturabo/Angron/Curze are all broken and accelerate toward their own dooms despite Horus becoming Warmaster;
1) Perturabo, Angron and Night Haunter remain fully functional generals long after Ullanor.
2) Horus recognized the best way to utilize Legions like the World Eaters and Night Lords, would Guilliman? By which I don't mean: Can Guilliman recognize the best strategies for them, because of course he could. I mean: Would Guilliman allow those Legions to continue functioning in the manner they are designed to, would he allow them to use the strategies they've come to embrace and depend on? His reaction to their 'excesses' leads me to think he wouldn't. But neither Angron or Night Haunter would be swayed on this, both recognize their roles and both have fully embraced them. Do you think they'd take kindly to goodie-two-shoes Guilliman telling them they're wrong? Horus knows how to make broken pieces work effectively, does Guilliman?
Papa Smurf is also smart enough strategically to actually see the patterns Lorgar was creating to undermine the Imperium if he was placed at the center of command. The Heresy would still have happened, but it would have been a 2/3 loyalist 1/3 heretics war.
What 'patterns' was Lorgar creating? The Chaplains were a recognized and fully instituted part of Imperial policy. The Lodges were a far more covert thing, and I don't believe any existed beyond the Legions that turned, so there'd be no reason to expect Guilliman to be more aware of them. Further, the Heresy as instituted by Lorgar is a war unlike anything Guilliman had ever seen before. He's smart, yes, but is he smart enough to see something that literally no one else (not even the Emperor) saw coming?