A lot of us have come up with such explanations, and they deserve to be taken as seriously as the theist claim. One of the most common explanations is simply that human beings are prone to attributing animacy and agency to physical objects and forces. Theism is ubiquitous, but animism is even more widespread around the world. People mistake inanimate objects all the time for animate beings (See anthropologist Steward Guthrie's
Faces in the Clouds). Forces of nature have always been mysterious to primitive cultures, so it is no big mental leap to conclude that intelligent agencies are behind them. And maybe that hair-trigger tendency actually has some evolutionary (survival) value. Hence, the tendency to personify inanimate forces--to see controlling agents behind natural phenomena--leads to widespread belief in gods. So, when people experience extreme emotions--awe, fear, wonder--they can naturally jump to the conclusion that they have had a "divine" experience, when, perhaps, all they experienced was a flood of endorphins in the brain.