> There is a very real perception among them that the scriptures allow a better understanding of nature and the universe than the systems nature and the universe provide to aid our understanding.
That is mostly true in the west of a new variant of Christianity - American evangelical Christianity. It only really really took off in the 18th century ( https://en.wikipedia.org/wiki/Biblical_literalism#History ) and has gained a lot of ground in recent decades. TO some extent I think it is a product of the same culture as political ideologies: polarisation and blind loyalty. Like those ideologies it originated in the US.
> I'd bet dollars to donuts that extremism in the future will be fueled almost exclusively by these quasi-religious political groupings.
It is already the case. If you look at the 20th century the most extreme violence was fuelled by fascism (secular, wanted to replace existing religions, some leaders like Mussolini were atheists) and communism (almost always anti-religious and persecuted religions).
I think maybe these ideologies opposed religions were because religions are rivals for capturing people's values and loyalties.