I would say, in response to the conditions caused by "authoritarianism and militarism of the czarist monarchy, the consequences of industrialization", not the ideas of industrialization, authoritarianism etc per se (i.e. a battle of interests not ideas. Ideas and ideology are built, or rise, upon those interests to legitimize them at a higher "noble"/abstract level). In the HoI case idealism is not so much about religion as it's about person (and ideal) centrism, i.e. the "role of the individual in history"/"Great man theory" and specific idea-to-action mechanics. From the get go Russia was quite religious (lots of religions, including islam and to a lesser extent buddhism), but the role of religion and even the belief in it got less and less important, until the 90ies, where it yet again began to serve as a specific pain killer, for good reasons. From a govt point of view, it's a kind of common uniting idea, now that socialism isn't. I would say that's a good background for spiritual civs, but not sure if a truly space faring -humanity- could be religious in the organized sense, by then, due to the likely associated absence of preconditions that may have to exist for (organized) religion to be a viable thing. It's a bit like the Skyrim issue.
Re: Edit : That kind of spiritualism ends up in idealism, and is idealism at its core, hegelian or not. (Geist = spirit)
The idea is that the world is material in one way or another (i.e. there's nothing else).
But yes, IF they just got the laws wrong (tooltips and descriptions do not seem to support this though), then it's no prob, and the materialists should be able to research it just as well (but they can't!).
Tooltip for the hardline spiritual:
"Our science has proved that Consciousness begets reality. We regard with patience the childlike efforts of those who delude themselves it is the other way around, as they play with their blocks of 'hard matter'."
Materialist (not the hardcore - its description is not to the point):
"As we reach for the stars, we must put away childish things; gods, spirits and other phantasms of the brain. Reality is cruel and unforgiving, yet we must steel ourselves and secure the survival of our race through the unflinching pursuit of science and technology."
This is idealism ('spirituality' is for a lot of reasons a good enough substitute) vs materialism.