How and why did theological materialism develop?

Genes and culture developed to bond people much like a family, the real forces of human social behavior work along the same lines as pre-existing biological forces in a sort of feedback loop between biology and culture. Then the natural environment affects the way genes and culture express themselves.

Cultures also change because natural instinctive desires for success in survival and reproduction cause men to manipulate cultures in the attempt to advance themselves and their own groups. And so different religions and philosophies and cultures change and evolve.

The best religions and philosophies contained the most harmony with real human nature, that is, they affirmed, and bonded, the natural human behavior of being kin-centered, gender defined, age-graded, heterosexual, marriage-making, hierarchical, ethnocentric, even xenophobic, and religious-making, among other things, with group-selection as the primary unit of successful selection, followed by individual selection. That was and is the base of conservatism.

Religions, philosophies and cultures can operate for a time with behavior and beliefs that go against nature and human nature, but religions, philosophies and cultures are eventually pulled back by the biological/genetic leash of real human nature to cultures that better reflect real human nature, and then humans work within and adapt to the environments they find themselves living in.

Paganism contained many elements that bonded natural human behavior and real human nature, as defined above, but as we learned more about real nature and real human nature, religions, philosophies and cultures changed. The "revealed religions" and philosophies, such as Christianity and Hinduism, retained many of the bonds of past pagan religions even as they changed them.

Theological materialism is more or less placed in the ancient/modern worldview of philosophical naturalism, with the difference being that philosophical naturalism is generally irreligious, and theological materialism is religious in seeing Godhood as the goal of material evolution, first mirrored in the Father-Within of traditional religion, which is retained but transformed. (See more extensive reflections on theological materialism here)