I love when a manipulative character successfully manipulates the audience. Like the vast majority of takes I see about Lorgar on reddit are
-"Why is everyone so mean to Lorgar, he was a good guy who only became a villain through mistreatment, poor bullied Lorgar"
-"Lorgar's an easily malleable, gullible chump. What an idiot"
And its like...yeah no that's Lorgar's own narrative. You fell for his bullshit.
Firstly, he is not a gullible chump manipulated into heresy by Kor Phaeron and Erebus, he's fully aware what they're doing. Lorgar is very good at playing the naive pure soul, but in actuality he's leading them by the nose into suggesting the Terrible Thing he already wants to do because it allows him to avoid accountability. He didn't suggest it, it's not his idea, they made him do it. God bless plausible deniability.
It reminds me of when I used to be on insane diets as a teenager, I'd stare longingly at bacon until someone suggested I have some, then I'd protest until they "talked me into it". However, after I'd finally eat it, I'd complain "Well now I'm going to get fat, why did you force me to eat bacon. This is all your fault, how could you do this" (yeah I was insufferable, but so is Lorgar, that's my point: it's insufferable bitchass behavior)
I mean it's almost laughable that Erebus and Kor Phaeron could ever truly believe Lorgar is oblivious to their machinations: he's a Primarch. They're leagues smarter than everyone around them, to the point it's difficult for humans--or even lesser transhumans like Astartes--to conceptualize.
Then again, to be fair, there is a thing amongst con-men where they actually prefer to target white collar individuals with higher educations specifically because this often leads them to believe "I'm too smart to be tricked". Their hubris leaves them vulnerable and their ego prevents them from acknowledging they've been fooled. You see this quite a bit in Horus; he's a brilliant Primarch, but he keeps falling for manipulative bullshit because he's too arrogant to consider the possibility he can be manipulated.
But I don't think that's the case with Lorgar. I think being raised by a scumbag like Kor Phaeron has made manipulating and parsing manipulation second nature for him. He's surpassed his teacher long ago, and now Kor Phaeron is the one whose ego prevents him from acknowledging when he's been had.
There's a point in The First Heretic where Argel Tal is insisting something along the lines of "This is not the Aurelian's idea, he's too pure of heart and intention to ever suggest this, this plan reeks of Erebus and Kor Phaeron's schemes. Lorgar has issued the orders, but Erebus and Kor Phaeron are the ones who talked him into it".
This is exactly how Lorgar wants to be perceived.
In reality, he's a coldly utilitarian and calculated man with a "Many of you will die, but that is a sacrifice I'm willing to make" ethos. He'll do some performative weeping when he throws you to the wolves to achieve his goals, but at the end of the day: he doesn't regret it and he'd do it again.
However, he can't stand the idea of being seen that way, so he'll stand behind extremely unpopular men like Kor Phaeron and Erebus so they can take the heat instead. Lorgar likes to emphasize he's not a vain man, that his goals for humanity trump anything as petty as ego, but...yeah no that's horseshit, he is very much an egotist high on his own supply.
I also think it's telling when we get Guilliman's perspective on Lorgar; he sees him as an emotionally volatile, needy, petty and prickly lil bitch who loves pushing a "I am a good guy, yet I am endlessly bullied for no reason" narrative. This is an incredibly spot on read of who Lorgar is.
To buy into Lorgar's own Perpetual Hapless Victim narrative is, honestly, wild. Maybe it's obvious to me because I grew up in a family full of toxic manipulators. It teaches you to never only listen to what someone is saying, you need to take a step back and pay attention to how they're saying it, to how they're framing it. What do they stand to gain from this framing. What is their angle. In fact, it's probably a decent idea to just assume someone has an angle until they prove otherwise. It's a deeply cynical way to interact with the world, sure, but it does usually pay off.
Once you do that, people like Lorgar seem pretty transparent.