I think y'all are forgetting about Erebus, I mean he is pretty much responsible for turning Horus and therefore causing the Horus heresy
He is still alive, being as dickish as ever. Rumored he and Kor Phaeron locked up Lorgar in his tower so they could rule the Word Bearers.
I think hes more the idealistic leader, the nicer of the Primarchs, who would use Chaos to benefit mankind as a whole, rather than Erebus or Kor Phaeron, who only live to use Chaos to empower themselves. Lorgar in charge would mean the word bearers would be trying to serve as maybe a chaos version of Ultramar, an Empire founded on the beliefs of the chaos gods, but still good for the common man, while the other two just want to be in charge of a kingdom that only serves them. Stay in the Eye of Terror, get more and more followers through guerilla tactics, and in turn, gain more favor from the gods. Grimdark..... Note, this is all just speculation on my part, not sure what GW would say, but that's just the feeling I got from it.
