It's hardly an unreasonable supposition: the one definitely conscious entities we know of are also the apex intelligence of the planet.
To put it another way: lots of things are conscious, but humans are definitely the most conscious beings on Earth.
I can understand what less cognizant or self aware means, but "less conscious" is confusing. What are you implying here? Are their qualia lower resolution?
But that's not an answer. Why should intelligence and not some other quality be coupled to consciousness? In my experience, consciousness (by which I'm specifically talking about qualia/experience/awarenesss) doesn't at all seem tightly coupled to intelligence. Certainly not in a way that seems obvious to me.