Qualities of the human body and its psyche evolved to give an evolutionary advantage and so be more likely to be passed on and normalised.
There is a moment between sleep and wakefulness when a commanding voice may be heard, coming perhaps from a drama further back in the dream. It seems to be the sudden intervening authority of an awesome power.
Without the benefit of the hard headed skepticism, which we have also evolved as a species, it would only be exactly as it seemed – a presence and voice that moved though a veil from another world.
The digestive parts of this person, were perhaps at war with each other sparring and gurgling while the sleeping brain for its part had tried to withdraw amid troubling fears perhaps of relationships with loved ones or a lurking sense of mortality.
But after that moment, imagine how his authority and importance began to swell, to impose various doctrines and religious themes born for the adherence of others.
The whole charismatic show for a thousand years collapses apiece if you take away that moment he mistook his own mere inner voice for the interactions of a god.