In Dune, religion plays an extremely large role in the ongoing story of the fictional world. Frank Herbert's world building is such that a fully realized world is laid out before the reader, and like the real world, religion is very important. But what role does Herbert assign religion in society? There are many schools of thought as to why religion exists. According to Freud, religion existed as wish fulfillment. Religious people simply imagined a world that was structured according to what they wished the real world was like. Good people are always rewarded in the end, evil always punished, things happen for a reason etc.
In Dune, we see this idea with a bit of a twist. The Messianic Fremen religion, like all messianic faiths, has a strong element of wish fulfillment. The Fremen have been oppressed and abused for thousands of years, and they believe that once their Messiah comes they will rise up against their tormentors. This happens in Dune when Paul becomes the Kwisatz Haderach, the Mahdi, etc and the Fremen begin their Jihad against the Imperium. Arrakis becomes the Imperial home world and billions of people are put to the sword as the Fremen exhaust their blood lust against the galaxy at large.
The interesting part of this is that Paul sees that he is largely useless in this process. The Fremen need only think their Messiah has come to set the Jihad in motion, Paul actually being alive or directing them isn't necessary. If Paul dies it would continue under his mother, if his mother died it would continue under Chani, or Stilgar. If all these people died it would continue in his memory alone. Paul knows that once Sietch Tabr believes him to be the messiah in the Cave of the Birds, the rest is a foregone conclusion assuming only a single Fremen lives to carry the word to his or her brethren.
This tells us that it isn't the physical Messiah that is needed, only the catalyst. After all, the Fremen being so powerful there was no reason the Jihad could not have begun ten, or even a hundred years earlier. All they needed was permission to go about what they wanted. In this sense, their religion really was all about wish fulfillment, they didn't NEED a messiah, they needed only to believe their messiah had come to seize power.
