Has anyone heard of the Tyranids from the 40k universe? Similar to what you suggested, the story behind them is that they're bio-engineered monsters designed for war and consumption. They land on a planet, strip it of all life and use that organic matter to grow/birth/? more Tyranids to consume the next planet. All Tyranids are controlled by an immaterial psychic mind called the 'Hive Mind' which basically controls them and tells them what to do.
The monsters could be like that. A psychic alien mind wants to consume planets/kill humans/etc and has created the monsters to do this. This mind is telepathically controlling the monsters, explaining why they know how to destroy power relays in strategic locations. When a new (hunter) threat arises, the psychic mind grows a new breed of monster to counter that.
Also I bet some of the inspiration for Kraken's design came from the Tyranids, maybe the lictor.