First of all I have to admit that I really want it to exist. I have a vested interest, so to speak, in the continuation of my consciousness past my physical death.
Second, I would call a gradual revelation as rather influential. Starting with out-of-body experience (not mine) and continuing with communication with supposedly dead beings via channeling, both collective and then personal, and finally to the observation of coincidences in my life- first suggested that there exists a supernatural world containing intellegent beings and then to the mind-boggling suggestion that our lives may be controlled by something else. I still have difficulty with that one.
Finally, what originally made me an atheist was science. Chemistry ruled in those days. So I looked into science to see if there were any room for the supernatural. What I found was that dark energy and dark matter, the realm of the supernatural if one existed, was 99% of the universe. And there are particles axions with just the right properties to make the dark super.
Scriptural prophecy and cosmology was also influential.But much of the prophecy is yet to happen, unless you take WWII to be the Armageddon. And the prophecies that are reported to have happened could be historical revisionism.
Regarding the evolution of god, we should not expect a fossil record except of us. Presumably the supernatural world is not so different from the physical world in terms of there being work to do and aims to achieve and evolution to experience. There may be life and death entirely within the supernatural. Heaven as a place to rest may just be wishful thinking. Of course, the whole idea of the supernatural is also wishful thinking.