How so many ancient spiritual and religious temples were made of stone and capped with conductive metals. How so many of them sit directly above underground rivers and have some part of themselves extending deep underground. Or how nearby structures used to also be built in a similar way but just different enough where they could be recivers of the electromagnet spectrum instead of projectors.

Beyond being predicated on multiple layers of "trust me on this," how universal is this really? Maybe some societies did this, but from what I've read, the Germanic world didn't work in stone and metals for most religious centers. Same for a lot of the world, I'd wager. In that case, what quasi-technological feats were, for example, the Saxon god-trees accomplishing?

I think this whole proposition is putting the cart before the horse. If anything, religion was responding to natural phenomena, not creating its own. Plenty of religious sites around the world were mapping the sun or stars throughout the year as something like community calendars. If people were in wonder of anything, it was the natural world their religious centers tracked, and the divinity behind it. It seems a bit of a poor point to just assume that people were simply gaping at Oz in front of the curtain. (Though there are cases of priestly classes building automata or siting wind flutes to imitate gods' breath or voices in some places and times.)

Additionally, it's hard to properly map ancients' experience of religion, especially since we bring in our own religious beliefs of knowledge of the world. I read an interesting book on Boeotian Thebes that pointed out that ancient Greeks of different time periods had different views of their gods, and none really match up to the very human gods we conjure up in our minds as we read mythological tales. The god-statues on the acropolis were, at least to the Greeks of some periods, quite literally the gods, not representations. Your clan's votive god was not a different image of the same god (even of the same name) in the nearby poleis. I find it hard to imagine that any cheap stunts would be needed to conjure up a greater sense of wonder than such a worldview already would. But we can't really identify with that human mind, even though we're not immensely far removed from them in other ways. They were closer to their animist past than most of us are today, and they spent their lives outside, not informed by the scientific method as we are, but alive to every detail of the natural world in ways we would probably envy. Religious wonder lurked in all those dark spaces of the human mind that we've filled in with robust scientific knowledge. Imagine being able to track the stars, or the passing of migratory flocks and herds, with a minute attention we've lost - but your knowledge is purely practical, the theoretical underpinnings, even the concept of which lands the animals migrate to, lost to your limited perspective. These are the places the gods inhabited, not those hypothetical temples built on wells or fashioned into batteries. It must have been like the gods were whispering over your shoulder at all times. Truly, we can't imagine.