When the super carriers left for the Koprulu Sector, one was filled with animal lovers, namely the feline kind. They had lions, tigers, panthers, cheetahs, even house cats. However, when the carriers arrived, they crashed and the one with the felines fared no better. Having survived the crash of a super carrier when their owners did not, they began to learn from the audio and video logs left behind. Soon, the began to try and walk on two legs. By the time of the First Great War, they'd evolved to be human like in stature and hand usage, and learned, from reverse engineering crashed battle cruisers and such, how to create their own weapons and armor, emerging to shot themselves a force to be reckoned with. Their fleet is formidable, army determined and all armed to the teeth. The larger breeds proved to be the most effiecient frontline infantry, specialists, leaders, elite guards and other important roles. The smaller breeds, namely the house cats, grew to be the size of young adult tigers, and proved adept as engineers, medics, pilots, scouts, light infantry and other less exposed, but still important roles. Don't underestimate the Lion's Fury Imperium.
This makes sense. They won't gain advanced tech out of the blue, they'd reverse engineer it. Read it and weep gentlemen.