Why didn't the Cabal try to prevent Horus Heresy?

Question

In the accepted answer to the question What would have happened if the Horus Heresy hadn't happened in WarHammer 40k, it is explained that the projects of the Emperor would have been completed, that is mankind would have conquered most of the galaxy, spreading atheism and annihilating the existence of uncontroled psykers. Cutting the connection between the Chaos Gods and human beings would have extremely reduced their forces, to the point that they wouldn't be a threat for thousands years. The time for the Emperor to control the Eldar Webway to safely travel through outside of the Warp influence.

At the same time, the goal of the Cabal is to destroy the Chaos Gods. Their plan is to help Horus to win over the Emperor (by pushing the Alpha Legion to join Horus), since they foresee that in the aftermaths, renegade Legion will turn against each other and lead he destruction of mankind, and subsequently destruction of the Chaos Gods.

The success of the plan of the Cabal was far from certain (it actually failed). They acknowledged it when meeting Alpharius/Omegon to try to convince him to join Horus. Before the Heresy, the Emperor was about to succeed. So it seems to me that pushing the events in a direction favorable to the Emperor would have been a safer plan for the Cabal.

Is it explained somewhere why the Cabal didn't try to prevent Horus Heresy and help the Emperor in his plans? They just didn't see the Heresy coming? Or did they fear the power of an almighty Imperium of Mankind?

Answer 1

I think it gets easier when you look at the causation a bit differently: the Cabal knew that events were already in motion to force a Heresy-like obstacle to the Emperor.

Yes, the Emperor's plans coming to fruition would deal a great blow to chaos, however the Chaos gods are not dopes. They had been well aware of the threat and had been seeding their eventual response to the Imperium all across the galaxy since the primarchs were detected and scattered.

For whatever reason, the Cabal simply was not in the position to prevent the Heresy. The events of Legion are a few years before the fighting starts, but the Great Crusade itself is 200+ years old and Chaos has been scheming for at least that long. The Cabal knew Chaos was making a move years before the Heresy erupted, however they were either not influential or powerful enough to stop the threat. Unable to prevent the impending Heresy, the only option left to the Cabal was to control it and shape it to their ends. In the Cabal's estimation, the Emperor was doomed, be it the Heresy or some other vector, Chaos was onto him. Frankly, they were right, the Emperor's hubris/over-confidence left his blindspots (his sons) wide-open and the only play left for the Cabal was the "Horus burns down the galaxy and then Chaos itself" option. :(

Answer 2

I think your view of the cabal isn't correct. You need to understand that the cabal is primarily made up of non-human (aka alien) races. You should also understand that the cabal helped BOTH sides of the civil war. :Likely in an effort to ensure the mutual destruction of all humanity.

The Emperor's Great Crusade was a huge threat to all non-human inhabitants of the galaxy. The Crusade's intended purpose was to unite humanity under one banner while conducting xenocide on a galactic scale. The end result would be a galaxy that only had humans in it. Worse, the Imperium was highly efficient at this and it was obvious to everyone that He would succeed.

To allow Him to continue would mean the death of all non-human species. Sure Chaos would be under really tight wraps as well, but that wouldn't matter if your entire species was ground to dust.

Next, the cabal knew that humanity's next evolutionary step was to become a very powerful psychic force. Psykers are one of the primary ways that Daemons can cross over into the material realm.

This also had to be stopped otherwise Chaos would overrun the galaxy by simply popping through the potentially trillions of human psykers.

Now that you know that, you should see that the Cabal's primary goal had to be the total elimination of humanity. What better way exists to stop an unstoppable force than to have it turn upon itself? This one reason is why the various cabal agents alternated between helping the Imperial forces and helping the traitors.

Interestingly, Chaos wouldn't want to destroy all of humanity. Their goal would just be to stop the Emperor from succeeding in removing religion, so that they could more easily take over the growing population of psykers... In order to make that happen, they also wanted humanity to turn upon itself BUT to still exist afterwards.

With this understanding, it becomes obvious that Chaos won when Horus died and the Emperor was entombed in the Golden Throne. The establishment of the Ecclesiarchy has since allowed Chaos to thrive and the ongoing wars of humanity with itself, with other races and with Chaos have continued to feed the various Chaos gods.

Finally, here is the kicker, the Cabal had various psychic races amongst them. Psychic power is derived from the warp and the warp is the play stuff of Chaos. It's not really a stretch to believe that the cabal, in their hubris, were essentially Chaos pawn's led to stop the Emperor's plans. After all, the Heresy doesn't occur very long after the Eldar's own fall - and the Eldar were a big part of the cabal..

Answer 3

In Legion the Cabals explanation to Alpharius/Omegon is pretty clear.

If the empire with the Emperor at the helm wins Chaos takes over much faster and there is nothing but Chaos. If they help Horus then the encroachment of Chaos happens much slower, giving the cabal time to act. That is why Alpha Legion "turn" rogue. IMHO Alpharius didn't do what the Cabal wanted but choose something different.

Synopsis of Legion book.

7. Legion: secrets and lies

Legion features the "Alpha" Legion of Space Marines, the 20th and last to be formed. It is the most secretive, subtle, and inscrutable of all Legions; its deepest secret is the binary nature of its Primarch, who comprises the twins Alpharius and Omegon. The book also highlights the Imperium's mainstream military force, the Imperial Army, featuring several male and female officers and their units. Another important factor in the novel is The Cabal, a mysterious, ancient interspecies organisation opposed to Chaos – one of the main characters is a human Cabal operative, John Grammaticus. The story takes place over roughly a 6‑month period, about two years before the Heresy starts; it describes the events that eventually lead Alpharius Omegon to support Horus.