The Progenitors arrived at a relatively light, low gravity world, rich with life. They saw such entertaining species there and as such, decided to upllift then, just to see what they would do with their sentience. It was an easy project. A wave of a hand, really.
Two species came out as sentient. One of them was a relatively large and benevolent herbivore race, that mused on philosophy and theocracy as they drifted idly between algae-clouds, absorbing the nutrients into their jelly-like forms.
The other sentient species observed their actions and said "fuck that".
And so the strange nautiloids, with shells several feet in diameter and bodies several feet long, rose to dominance. On the soft earth, they were sluggish and slow. But when they soared through the heavens, they were graceful and majestic. Using beak, tentacle and the bodyheat that they had such magnificent control over, they subdued the prey species and drain their blood until they became lifeless.
As they grew in number, they developed. They began to enjoy the concept of excess - being able to do whatever they wanted, whenever they wanted, because they were the masters, and fuck whoever said 'they didn't need to'. They enjoyed sex, fine blood, both fresh and fermented, dazzling shows of heat and flame and wonderful, wonderful music.