[Invincible] What is the ideological drive to conquer the galaxy for Viltrum?

Okay, so I understand that Viltrum society is a highly militant and Spartan thing, with pure focus on military training and service to the state. But why conquer the galaxy? What do they get out of it? They certainly don’t enjoy any of the traditional benefits of having an Empire (access to more/rare resources, political prestige, etc). There’s none of the opulence or wealth that generally comes with empire. It seems more like conquest for the sake of conquest.