Karl Friston's free energy principle is probably roughly 80% of my reasons to think they're coupled. The rest comes from studying integrated information theories, architecture of brains and nervous systems and neutral nets, more broadly information theory, and a long tail of other scientific concepts (particle physics, chemistry, biology, evolution, emergence, etc...)

Isn't that begging the question? If you just accept the presupposition that intelligence is tightly coupled to consciousness, then all that makes perfect sense to me. But I don't see why I should accept that. It isn't obvious to me, and it doesn't match my own experience of being conscious.

Totally possible that we're talking past each other.