Did Herbert have a plan for this combo, or was he just making up some future backstory? Like sometimes happens when authors aren't really sure there will be a sequel at all, and just scatter some future references around.
Agree, and those evocative references were one of things I loved when first reading the Dune series many years ago as well as watching the '84 film. I still remember being taken aback at the reference to "Emperor Hitler" and the fact that knowledge of him was (rightfully) lost with time, but also along with most other knowledge of our era.
The ones that come to mind for me are Dan Simmons, Walter Miller, and Philip K Dick. If you remember the Priest's Tale from Hyperion or Mercerism in Do Androids Dream of Electric Sheep, you know what I'm talking about.
But I do also grok what you're getting at- ultimately these trappings of religion are part of the medium of power, and covers up the base desires of humanity, even when it becomes transhuman through space spice-psychic magic. Herbert's elaborate spiritual systems then become manifestations of the culture under religion, but don't hold true moral or philosophical significance that religion is supposed to have, because the true moral reality in his setting is ultimately still about power.
I don't know, I haven't read the sequels, this interpretation might be really off-base.
In the later novels it introduces the concept of "Arafel" a word which comes from the Hebrew word for darkness. It represents the apocalypse (the end of humanity) and the idea is that through the golden path humanity is steered away from Arafel, so there is a thin veneer of a moral justification beyond power..
zen buddhism can reasonably be thought of as a mix between daoism and buddhism
pure land buddhism is basically christianity dressed in buddhist language
modern hinduism is full of buddhist elements
many central aspects of christian myth can be traced back to things like the resurrection of osiris
many christian practices such as monogamy and christmas are obvious continuations of roman pagan religious practices, and of course 'easter' was a northern european fertility goddess (though she isn't the origin of the festival with her name; the corresponding holiday is called some version of 'pesach', 'passover', in non-norse languages)
in many cases particular saints in syncretic catholicism in the new world can be identified with particular pre-conquest deities
islam is largely judaism, but has clearly integrated a lot of non-jewish cultural elements
and all of that is just in the last 2500 years! so it seems totally believable that in 26000 years things would be vastly more intertwingled
Islam is just Judaism? What? Christmas isn't pagan. That's a myth. Modern Christmas was invented by German Protestants and then spread to England where it was given a huge shot in the arm by Charles Dickens. You're wrong about Zen Buddhism.
Syncretism exists, but Herbert is just so lazy. He mashes together two different religions with very little in common other than Orientalism (his greatest vice as a creator).
Personally I read Dune in my first year of university, when I was doing a course on the Middle East, so it all hits very different to me, and the Arabic in Dune is very important to my personal appreciation of it - but I can see how it's hard to introduce to a contemporary audience due to all the regrettable events of recent decades, so perhaps it makes sense. It seems impossible to make neutral references to Muslim/Arabic culture or history these days, everything becomes some grand political statement for or against Bin Laden or Salman Rushdie...
Overall I think the topic of religion stays vague apart from Herbert making use of the trope of a Messiah and using syncretism as a symbol that major shifts happened in the human societies that brought opposing religions together.
It has been a very long time since I read all the novels so I can't recall all the details. It is a major plot point in book 5 "Heretics of Dune" zensunni leads to the alliance between the Bene Gesserit and the Tleilaxian's. The Tleilaxu follow a strict interpretation of the religion in secret and during a meeting between the faction leaders one of the reverend mothers is able to deduce this from their speech patterns and manipulate them into an alliance which has some ramifications.
Considering the Tleilaxu aren't introduced until book 2 (I think) I assume it was planned out ahead of time by Herbert.
We don’t see face dancers or high level negotiation with the Tleilaxu in book 1, that I agree with.