You call it fantasizing, but that's dismissive and, frankly, small minded. It'll totally prevent you from understanding what you're asking about.

But, first, remember that you're asking questions from the outside, and I'm answering them from the outside too. Never been Satanist, never will be. So this is meta as fuck here. Don't get shit twisted though, and we'll have a fun conversation about it. You don't have to agree, accept into your own beliefs, anything anyone else does, but if your intent is looking for reasons to dump on the subject, you'll just end up bored and ignored.

my question is about the need to "divine".

Because that's what spirituality is. It's the search for and exploration of a non material aspect of the universe. Everything from monotheism to ceremonial magic to zen meditation is a pursuit of something intangible.

That pursuit may or may not be something that changes anything in a concrete way, but when pursued consistently it changes the way people think. It isn't something you can dismiss as fantasy because fantasy doesn't and can't change anything other than one's imagination.

What that change is, in spiritual pursuits, varies. But it's the goal. People looking for the divine in themselves and the universe are seeking to be other than "just" a part of material life. The rat race, the grind, the orphan crushing machine, the empty and draining toil that is survival. People want life to be more than that.

Divinity is the opposite of materiality. It's the spark of sentience and sapience. The mind of the universe that peers out at itself from inside everything. At least, that's the general purpose version rather than religion specific one. Looking for that externally has its benefits, as adherents of the various theisms will point out. But looking for it inside the self does too.

In seeking the inner divine, the individual seeks to become closer to it, to live closer to it. To seek the divine in the self is to seek expressing that divinity. The closer you get to god, the more the light of god can shine through you. You reduce the more primitive drives and embrace "higher" ones that are about being a source of positive change, a source of goodness (though I'm dubious the goodness exists as a discrete face of reality personally).

That's why the divine. The divine is just a code word for a better state of being. It's an expression of seeing an underlying connection in all things and venerating that connection.

Know thyself, when pursued to its natural extent is the pursuit of the divine self. When one knows oneself fully, one ceases to be in bondage to the physical self, and gains the perspective of a "higher" self.

Now, I don't necessarily think that the physical is lower or lesser than the spiritual or mental. Kinda the opposite, in my own little world view. But most forms of spiritual pursuits do at least handle the physical as being a state to escape, suppress, or overcome. Pain, fear, greed, anger, all the unpleasant stuff that goes along with the material world seems like something to escape, so you run into a lot of systems of spirituality that throw the baby out with the bathwater. At least, that's how I look at the rejection of the physical entirely.

Anyway, with that tangent aside, "when everything is god, nothing is god" is exactly the same thing as "thou art god". When one sees divinity in all things, one realizes that there is no external deity. Thou art god. I art god. My chicken art god. We aren't separate, unfathomably disconnected things, we art one. That's the whole point of it.

Thus, spirituality seeks to embrace that lack of disconnection. To bridge the gaps between.

That isn't fantasizing. It's a pursuit of self development.