system
Given the following post, respond as if you're commenting on Reddit:
human
[40k] What would have happened had the Primarchs note been scattered?

Had the Primarchs not been scattered across the galaxy at their creation and the Emperor had trained them from birth, how different would the outcome of the last 10,000 years have been?

Would the Imperium be stronger / weaker? Would the heresy have occurred?

What would the state of the galaxy be?
gpt
The Heresy would likely never have happened. Lorgar's corruption by Chaos is beleived to have happened on Colchis, and it was Lorgar who finally swayed Horus to Chaos (with some help from the Davinites). 

Had the Primarch's never vanished from the Lunar Gene-Labs, Lorgar never would have been indoctrinated by the Covenant. The Primarchs never would have been touched by Chaos, and the Imperium would be a very different place.