I read the comics so I’m not afraid of spoilers but it’s been a while so remind me if I forgot anything or if they explained it already.
Most empires expand to explore new world, gain strategic resources, visit new things, or even gain new cultures or customs. The viltrumites has been stated as been like the most perfect or powerful species in the world and they already don’t need to really eat are extremely powerful and advanced technology and can freely visit any planet with ease. They don’t care about other cultures, technology, food or knowledge or really need other resources, so what’s the point of expanding? Why have an empire? Why not just explore the galaxy and be not be just absolute bullies? What’s the point?
Yes I would argue that, but human planets in warhammer 40k are extremely dense and always need of more legroom to grow. Idk much about the warhammer 40k except that been a foot solider is one of the worst positions in galaxy
my point isn’t how similar their empires are, but their mentalities. 40k humans would absolute conquer the galaxy just to genocide xenos for their supremacy IF they had the strength of viltrumites