That’s just Lovecraft, I think. He was breathtakingly, paralyzingly terrified of everything from seafood to air conditioning. The man never encountered a concept which did not inspire some deep-sated cosmic horror in him. When his stories work is when, just for a moment, he’s able to share that fear with his reader. But most of his stories don’t actually depict events which are all that scary. Think about them too hard, and they stop working."There is nothing more merciful, I think, than the inability of the human mind to correlate its contents." Or however that Lovecraft quote goes.
But let's be straight: There's a giant psychic squid monster on a sunken island in the Pacific. Conventional weapons are useless against it. One day it'll wake up and that's gonna suck, sure. Not particularly incomprehensible, though, however much we might not want to think about the prospect.