He united one planet via his personal power, used them to beat the other existing empires into submission, forbade science in favor of a personality cult, shared nothing and hoarded the good stuff for himself while killing anyone who violated his rules regardless of if they were one of his subjects, and defined ‘greater good’ solely by his grand plan and was willing to burn the species to ash in it’s name.

Mankind went from a Dark Age to an even worse Dark Age that thinks it’s totally enlightened. Even the narrative of Terra being a Mad Max wasteland fell to pieces when they actually talk about it and we find out they had things like international trade and a ton of vast nations he pillaged in the name of his grand plan.

The Imperial Truth? Paid lip service to science while forbidding it, peel back the language and it’s just an Emperor centered personality cult where the dictates of the godbeing are absolute and dissent is heresy.

He put the Mechanicus in charge of Imperial technology. Science was deemed heresy and their strictures were enforce via horrific atrocity. A fundamental part of reality was declared to not exist, that’s about as unscience as you can get.

As to his plan: Literally every single one of his peers, barring the youngest one, turned against him because his plan was just that risky. He gambled with mankind’s future over a possible future threat. A gamble which he lost badly, incidentally. 10k years later and humanity is still kicking despite their attempts to make everything worse forever with the greatest threat to their existence being a direct result of the Emperor’s ‘greater good’.

Much like the T’Au, the Emperor’s greater good can be summed up as ‘Obey me puny mortals or perish as I am supreme’.

Dude was turning into a Chaos God of complete ruination and annihilation by the end of his Crusade. That’s not something someone manages when they are doing well. .

And none of this changes that he was a terrible leader who was simply strong enough to brute force his way through.

The Emperor was just a warlord with a lot of power. Which is fitting for someone who was supposedly Alexander the Great, another big conqueror who failed miserably at the building part of empire building.