User blog comment:DYBAD/Character Sheet/@comment-24955665-20180718090850/@comment-4867780-20180721134458

Basically everyone is a slave to their nature, as it determines everything we are, feel and desire, and are actions are in turn determined by those. I don't think the Horus Heresy was part of any grand plan on the Emperor (though it would have notably explained the puzzling numerous misakes that eventually led to it) seeing how globally disastrous the outcome was, that or things went reaaally off-plan along the way ^ ^;

Lawrence would definitely point that his repreatedly less-than-caring attitude towards his devoted sons at crucial moments is what eventually led to their corruption and full-on betrayal, though he would be understanding himself of the Emperor's circumstances, extremely busy in general and highly focused at the time on a revolutionary project that would have secured the future of the Imperium, project that had to remain a complete secret for the Chaos Gods would have thrown all they have to stop it once discovered.

Since the Emperor's spiritual form was in the Warp when the Chaos God were so easily wiped out, he would be fully aware how incredibly powerful Lawrence is, and that breaking a formal agreement with such a towering entity would likely prove a mistake of apocalyptic proportions. A large part of the Emperor would rather have nothing to do with him and just forget his existence altogether, so terrifying the thought he may judge humanity like he did the daemons, yet the unhopped-for and truly miraculous opportunity to finally return to the physical universe in his prime and save his crumbling Imperium from itself and its countless ennemies would be just too irresistible to pass.

So in the end, he would likely accept the offer on the condition that Lawrence promises not to terminate mankind as long as the Emperor lives up to his end of the bargain (reasonable compromises towards peaceful coexistence), securing both his physical resurrection and following restoration of the Imperium, and relative mid-term safety from this greatest threat.