1. Ignorance: total lack of knowledge about something
2. Doubt: learning something, but not being sure of its validity
3. Belief: learning increases to the point where one will defend their point of view

From there, come two paths:

4. Scepticism, or scientific method: constant gathering of additional knowledge to support one's beliefs, without ever abandoning all doubt, iterating over steps 1, 2 and 3
5. Faith: accepting some beliefs as absolute truth, without any doubt, without need for further proof

This is where grifters and wannabe leaders come in.

Once doubt is abandoned and no further proofs are needed, it's easy to convert someone's ignorance straight into belief, then into further faith. They don't need to prove anything, so can make someone faithful believe anything, just by building onto their belief's narrative.

Some call it the 70/20/10 rule: present someone faithful with 70% stuff they believe, along with 20% something they've heard about but don't understand, and the remaining 10% they'll swallow hook, line and sinker, no matter what it is, happily including it into their own beliefs.

Grifters use this just to get some money: they tell you 70% something you believe in, 20% something that sounds "cool"... and the remaining 10% is the price you need to pay.

But wannabe leaders take it a step further:

6. Cult: once a group of people faithful to the same beliefs is gathered, a leader can use the 70/20/10 technique to build out everyone's beliefs at once
7. Sect: among those beliefs, a leader introduces the captation of new members, delegating their job and growing up the organization
8. Religion: with enough beliefs, and faithful believers, a corpus of rites and rules can be established, that believers will follow on their own to reinforce their faith in those same beliefs, removing the need of constant "micromanagement" from their leader

Over the years, as you said, new wannabe leaders latch onto the established religions, they already have most of their job done, just need to follow the accepted rules for long enough to be recognized as the next rule maker themselves.

I don't see it in itself as an inherently "religious" thing

It is in the sense that faith is the basis of every religion. Without faith, without rejecting doubt, the rest falls and crumbles. So religions make sure to keep that faith going on, and cast any doubt away. That faith, is the real danger.

For a new grifter in town, the easiest tactic is to find the faithful, so they check out any Religions and Cults. They don't want Sects, because Sects are being actively monitored by some already experienced leader, but latching onto the beliefs of some Religion, or some nascent Cult, are the easiest "unmonitored" targets they can find.

Then just parrot back 70% whatever people already believe, add 20% some exotic and cool sounding stuff, and put a sticker with a price on it.

[source: I've had my dose of Religion, I got into a nascent Cult, even got offered to help grow it, left it just in time, saw the tactics used, saw them over and over in a dozen other Cults, saw the grifters flocking like vultures to them all... saw the faithful they were feeding on, and how some of them ended up, jumping from Cult to Cult until they ran out of money, friends, family, and finally their own lives. Then I saw other Religions and Sects, and the patterns are exactly the same everywhere. I thought I was happy, that I had friends... it was all an illusion, the real friends fell prey to it all.]