Macragge lay in the central region of the Ultramar Five Hundred Worlds. In the days when Guilliman was absent, it was generally managed directly by the lords of Macragge and Marius.
Because they had no need to pay taxes to the Imperium, every world in Ultramar was extremely prosperous. Guilliman had set up several relatively unusual administrative models for them; here, the Astartes, who originally took no part in politics, could be given political responsibilities.
Of course, after the Horus Heresy ended, Guilliman actually no longer intended to let the Astartes rule over humanity. But he also had no way to remove the Astartes' influence over the political power of mortals in a short time, not to mention that afterward he was placed in a stasis field.
What I mean is, if you were thrown into a living coffin that barely maintained your vital signs, what else could you do? Dream?
In short, by the time he woke up, Ultramar had already become a prosperous world jointly governed by its lords and the Astartes. He could not find anything to criticize, and besides, even if changes had to be made, now was not the right time.
Still, it was not as if he had done nothing about Ultramar after waking.
For example, the return of the Four Heroes System, and that time with his Thunderbolt Fury.
Do you still remember that rare moment when he flew into a rage aboard Macragge's Honour?
The lords of the Ultramar Five Hundred Worlds, for reasons known only to themselves, wanted him to change his title of Imperial Regent—if you do not know what that new title was, I can remind you on their behalf: the first two words were Second Empire.
In short, his current impression of the lords of Ultramar was not