The semi-autonomous part isn't that unfamiliar.

I don't need to concentrate on finger or hand movements while I'm typing this. My brain thinks about the words while it delegates the details to other systems. There's an incredible amount of processing involved in operating human limbs which we're mostly unaware of.

I'd guess octopus consciousness is similar - goal oriented, with delegation. I'm mot sure, given the relatively small distances involved, if the slight physical separation of the central and distributed brains would make a huge difference to having an all-in-one model with distinct areas squished up inside a single unit.

But I absolutely agree - they are amazing and fascinating. If they were more social they'd probably be running the planet.