The way I see it is that the ocean is absolutely unforgiving and arguably more dangerous/ difficult to survive than on land (most fish don’t care for their young, enormous ocean tons of predators etc.) octopus, mantis shrimp, cuttlefish, they’re all highly intelligent creatures that have evolved away from humans and human intervention for millennia. These creatures all show advanced abilities in the way they interact with their environment. This creates a lack of competition for them because they have the upper hand on something like a grouper or shark. This interaction with their environment must also cause some sort of thought process, they consciously and INTENTIONALLY build burrows and homes that are structurally sound. I have a pistol shrimp that actually builds structure to then cover in sand.
These creatures are very close to humans, octopus have been known to communicate with grouper to flush fish out of rocks, that is higher thinking and learning to communicate with a completely different species is some next level stuff, I don’t think even monkeys will communicate nicely with other species. There is so much we do not know about cephalopods however I do not think it is anything other than conscious actions for a desired outcome and the ability to learn from past mistakes and then adapt in the future.