Fair point, but surely it's more coherent to view that as a new state consolidating its power base by eliminating the opposition, rather than as a religious thing?
Depends on how it's done. If you take Stalin for example, you had the combination of a Cult of Personality
and the creation of a civic religion - any criticism become heretical, any crime was a sin. It tapped into the latent power of 'relgious' belief; where communism was supposed to be a society of critical thinkers, it became a society of creed followers.
The central problem is that, as with religious types, many on the left believe, utterly believe, they have found not just 'a' truth, but The Truth. While you can argue that even the simplest tory would claim the same thing, when they came to express their idea as Truth, they would fail, spectacularly. The left, OTOH, have a system of thought and argument that's easily as comprehensive and impervious to criticism as the Jesuits - and impervious in a way that goes beyond anything our hypothetical tory could muster!
When you say 'a new state consolidating power' you're abstracting a
human process. A state can consolidate it's power in many ways, but historically, the myth-making power, not to mention the emotional grip, that being able to tap into that bit of the human psyche that demands a grand narrative, that seemingly
needs something 'higher' than the individual that isn't material, of 'religion' is the easiest way to go...for a few years anyway. I mean what's easier for a new state to secure itself - a smart, critical population that views government with it's head, or one that unites around cues to emotion and is trained to view government with it's heart?