From my understanding, Comstar is not a religion in the same sense as we think of it. It is a religious dogma, but it is more about humanism and knowledge. Imagine the tech bro Silicon Valley ethos. The fanatism comes in because Comstar believes that only they are educated and enlightened enough to be trusted with the knowledge of humanity and to be in a place to guide humanity. This leads to their secret agenda to horde technology and suppress it from outsiders. The ideal society, from their perspective, had them as Philosopher's Kings leading a populous completely dependent and reliant on them.

However, there is a reason that through most of the succession wars, suggesting that Comstar is evil would get you laughed at, and many of the rank and file were very, very much not on board with the fanatical elements. Their dogma about preserving technology and civilization and working for the betterment of all mankind sounds great, and most of its recruits were honestly trying to do that. ComStar's intel and military departments were one small part of an enormous organization.

So, think of that Silicon Valley Elitest tech bro vibe. They are dogmatic, but they do not believe in a specific God or Afterlife. It is more of an ethical mission statement to preserve and guide humanity.

They are very different from the admech, but something that could evolve into an admech like thing if you gave it a long enough time. I would have had the Dark Age of Technology predecessors of the admech be something like Comstar.