A perfectly plausible story but society is so complex it’s probably unrealistic to pin it all on just that phenomenon.
Its not a unique story. It follows the typical religious sect proliferation mechanics that are seen in any other country.
> it’s probably unrealistic to pin it all on just that phenomenon
This phenomenon is the head that decides the direction of the broader American conservative spearhead groups from Reaganites to later 'Tea Party' types. They are pretty much meshed with the Evangelists now though, hard to tell them apart.
What I said above is true also, but does not say anything about religion. So how can you say that the reason for loss of rationality is caused by the group you mention, rather than the expansion of capitalism as I have mentioned?
My point is that we can say something that is definitely true but that does not prove it is the primary cause. Proving something is the primary cause in a complex system is extremely difficult.
These are the very lot who pushed all the deregulations and created the movement to go back to 19th century capitalism by dismantling what little social democracy the US had. So if you approach it from that angle, they again come up as the source of the problem. Of course, the mechanics of the phenomenon are self-reinforcing: This religious lot deregulating capitalism causes more poverty, and poverty pushes more people to the arms of religious sects like them for support and aid.
This kind of overcomplicating the problem makes finding the solution more difficult. Regardless of many smaller factions converging in different major groups in the US, the general, society-wide dynamics follow a given pattern. This pattern is exactly the same with the religious sects or far-right nationalist cliques taking over societies that suffer from extreme inequality and strong influence of religion.
In fact, I would suggest to simplyf the picture even further:
The mid 19th century dynamics in which the anti-intellectual, religious lot that populated the middle parts of the country, the east coast, 'old money' type aristocrats dominated the eastern part, and the nascent Californian West that wasnt able to put itself to somewhere in that spectrum, still are the major factions that collide with each other in the US.
Birchers started the movement to roll back the scientific, enlightenment ideals and left wing egalitarianism that got strengthened due to the scientific revolution and the popular movements succeeding in pushing left wing social and economic policies after World War II. It grew into Reaganites. Then when it was losing steam, its spearhead morphed into Tea Partiers and then Trumpers.