H. P. Lovecraft's psychology I think has to do with rejection of what is transcendental, and personal reality beyond just the ego. High disgust sensitivity-- if the universe couldn't be what one wants, if it doesn't have a familiar structure, it was a horrible abomination. It's an immature way of seeing things, but on the cusp of enlightenment.
Not saying I dislike what he did, his art was in and of itself transcendental, and describes a feeling of alienation that has become almost universal. Most intelligent people begin to perceive the prospect of ego death on some subconscious level, and many of them go on to perceive themselves in a very different way as a result-- something that, as far as the subconscious is concerned, is horrifying, eldritch. H. P. Lovecraft's work symbolizes the mad thrashing of your ego upon realizing that you are a much larger being than you ever knew. The ego is not the sole actor, nor does it really even want to be. That's where the feelings of smallness and irrelevance come in.
And this knowledge is perceived as irrevocable corruption, something that separates you permanently from the small world you knew as a child. Once touched by it you can never go back.
I'm skeptical of the idea that we gave God a human face as a way of giving ourselves universal relevance. We have always had to contend with things bigger than us-- predators, nature, the damned weather. We are adapted to navigate them. They just become part of the landscape, and we don't automatically personify them. So, God must have a human face for another reason... and I think that it's because it is something to strive towards. It's a reflection of our ideal selves, of the moral and cultural reality we value.
Lovecraft's Gods have mastered the truth that Lovecraft valued, as a lover of science, but have become something other than human as he knew it in the process.
I think with Lovecraft's stories, and with dark fantasy influenced by it (Warhammer, for example) we may be witnessing new archetypes forming. I think it's nihilism, the kind that infects people like Mama Merkel or the SJW hordes, ones who wish for a cessation of existence-- and make a damn convincing argument for why it should be the case.
You can't just kill these monsters, because they invalidate your existence just by interacting with them. They infect your soul, drive you mad. If we're going to formulate a hero that can deal with such things, it has to be a very different kind. The God Emperor comes close, with embracing his own demonhood to have a chance of standing toe-to-toe with them, but it lacks any sentimentality. Without that, it's too easy to think it's better to just not exist at all. The God Emperor kicks ass and all, but it's not a world you want to live in.
(Yes, I know WH40k is meant to be grimdark, but the old fairy tales were grimdark too before we formulated a way to deal with the problems they presented. It isn't that society became gentler that the fairy tales started having happy endings-- it's that we got a better hold on our reality, so a happy ending didn't seem like so much of an ass-pull. I honestly think media like WH40k is the new fairy tale-- our collective attempt to figure out how to fix our world and live in it.)