Peak oil is based on physics; the "religion" part involves what happens given a peak.
For the first part, if you have a limited biosphere, then you automatically experience diminishing returns when extracting resources from it due to physical limitations and gravity. You can see the same thing happening with mining:
https://www.youtube.com/watch?v=TFyTSiCXWEEThe problem's the effects: if prices go up through speculation, diminishing returns, or both, then economies crash, leading to prices going down. That deals with the speculation but doesn't reverse diminishing returns because no matter what the costs and prices are in dollars, the amount of energy needed to extract oil remains the same and has a downward trend.
Thus, economies fall apart due to speculation, and then can recover if more funny money is made, with people thinking that there's no more peak oil, but the energy returns remain the same and still go on a downward trend, which is what peak oil's really about.
Technology can be developed to counter diminishing returns, but as demand goes up, necessitating increasing production, then that counter becomes temporary. It's like extracting more oil to come up with 1950s products, and thanks to lots of oil, thus allowing for 2000s products, in turn leading to more oil needed.
This allows us to see the other part of that religion: the desire for a space age. People aren't happy with just seeing their warlords having chariots, or themselves having chariots. They want Teslas, or maybe fly in craft like the Jetsons. In short, they want more stuff each time, and better, too.
This puts to question the belief that there won't be peak oil because there'll be peak demand. What's likely is that peak demand's a religious belief, based on the premise that the current world's a feudal one and that plebes won't demand and get more, or that people will be perfectly happily to follow the WEF and own nothing amidst and technological utopia.
In short, following the thread on EVs, car companies need to sell more EVs each time, the IEA will tell people that peak oil's solved because of EVs, environmentalists will argue that EVs will solve climate change, and the WEF will say that people will happily just rent EVs. Also, they'll all say that the world's not far away from what they wish because it's already industrialized thanks to technological "gamechangers". That's what they see when they look out their window in the U.S., Japan, and Norway, with the latter often used as an example for EV use.
If any, that's the religion part. The non-religion part is that EVs require a lot of fossil fuels, can't replace ICEVs, involve cheap labor and resources from most of the world, which isn't like Norway but want to be like the U.S., and probably Norway later, which means the opposite of peak demand, as most of the world isn't industrialized but want do so.
And the elite who control the world aren't feudal lords but capitalists, which means they maintain power by industrializing that world.
Which is why they keep saying that peak oil is a religion because the world's doing well, EVs will save us, climate change is fake like peak oil or easy to solve, that people will be happy in a world that is close to and will be like Norway, and that new technologies will help them along the way.
Finally, most people want that world, which is why they don't like participating in peak oil forums, and wouldn't concerning climate change as well if it were not for celebrities connected to that issue and the environment.
In which case, I leave it to the few who are still studying that matter and figure out the points I raised above, then look at it through the lens of realism rather than what the UN, the IEA, the WEF, large corporations, capitalists, and pundits say.