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[DUNE] Who were the conspirators mentioned in Appendix III?

In the third appendix of the first book, there’s an intelligence report that outlines the (many) failures of the Bene Gesserit regarding their loss of control over the Atreides bloodline and the Kwisatz Haderach

“Here follows an excerpt from the Summa prepared by her own agents at the request of Lady Jessica immediately after the Arrakis affair. The candor of this report amplifies its value far beyond the ordinary.”

The gist of the appendix is that the Bene Gesserit fucked up so many times, and missed so many blindingly obvious hints, that it almost certainly means they were being manipulated by some outside group for unknown purposes. 

“Regular” secret societies and conspiracies bungle things all the time, but the Bene Gesserit are consistently portrayed as being super humanly disciplined and perceptive. 

The report ends by concluding that 

“In the face of these facts, one is led to the inescapable conclusion that the inefficient Bene Gesserit behaviour in this affair was a product of an even higher plan of which they were completely unaware!”

This sounds like an excellent sequel hook - the whole thing was a secret plot! 

Except Dune Messiah skips ahead 12 years and it’s never again hinted that Paul’s ascendancy was somehow orchestrated

Were Jessica’s agents just unduly paranoid? Like, they simply couldn’t believe the superhuman Bene Gesserit could have messed up so badly, so they started seeing malice where there was only incompetence?

Or were they right, and the Bene Gesserit really were being manipulated by some third party? And if so, by whom?

Can’t be Shaddam IV and his Imperial agents. He had no idea about any of this Kwisatz Haderach stuff. Likewise for the Harkonnens, the Fremen, CHOAM, the Landsraad

The Guild could possibly have foreseen some prescient disturbance, but they’re consistently portrayed as rather useless parasites who squander their true power. It’s unlikely they’re capable of subverting the Bene Gesserit

I think that just leaves two possibilities. 

Count Fenring was part of the Kwisatz Haderach breeding programs but he was rejected because he ended up a eunuch. He looks like a joke, but he was apparently one of the deadliest fighters in the Empire, and was very adept at scheming with his Bene Gesserit wife. At the end of the first book, he could have easily killed Paul as Shaddam IV ordered, but chose not to, apparently feeling a certain sense of kinship with him as a fellow Kwisatz Haderach

Did Fenring (and maybe his rogue wife) interfere with Bene Gesserit decision making and intelligence regarding Arrakis and the Atreides? Did Fenring know Paul and Jessica were alive with the Fremen, and did everything in their power to shield them from the Bene Gesserit? Perhaps as part of some revenge plot against the Bene Gesserit, or solidarity with a fellow mad science project, or just disgust at the idea of a Bene Gesserit controlled Kwisatz Haderach superhuman oracle?

Or could it have been the Tleilaxu? They’ve apparently bred their own Kwisatz Haderach prescient extradimensional superhumans, though they used genetic engineering and clone vats (axlotl tanks) instead of using the selective breeding of space aristocrats like the Bene Gesserit did. However, all of them proved to be uncontrollable and quite mad, and had to be put down. 

Did they know that the Atreides/Harkonnen bloodlines were on the verge of producing a Kwisatz Haderach? And if so, were they the ones responsible for sabotaging Bene Gesserit decision making regarding the Muad’dib religious movement on Arrakis? 

The Tleilaxu had Face Dancers - though trained Bene Gesserit could see through them, they might just be enough to infiltrate and subvert the Sisterhood, causing them to lose control of the Kwisatz Haderach on Arrakis.

This opened the possibility for the Tleilaxu to seize control of Paul and Alia years later, during the whole Hayt/Chani debacle in the next book

So this gives Fenring and the Tleilaxu the means and motive to be the conspirators behind the “higher order plan” mentioned in Appendix III. Was it either of them? Could it have been someone else entirely? (assuming original Dune canon only, no XD canon with Thinking Machines and Norma Cenva and whatnot)
gpt
The report lends itself to another reading, in which the Bene Gesserit sister who wrote it refuses to acknowledge that the Kwisatz Haderach could have arrived off schedule and outside the Sisterhood's control due to something as mundane as Jessica giving her husband the son he wanted, instead of a daughter.  

This saves face for the Sisterhood by casting them as victims of an attack, instead of micromanagers who fumbled on the 1 yard line and let a master plan generations in the making slip through their fingers.

It's worth noting that the report, which effectively clears Jessica of responsibility, comes at her behest after she had become the mother of the new Emperor.  That she has enough pull to influence the Sisterhood's written history of the affair speaks to just how far in status she eventually climbed from her days as a breeding program brood mare and then a widowed refugee.