well strictly speaking if he's advaita doesn't meen he believes in "god" (advaita is non dualism, and that can, in our sinchretistic times, easily be conneted with a sort of materialistic monism) and, well buddhist don't believe in a God as a personal path to salvation, and one can be an atheistic buddhist - no problem.
My guess is that he explains buddhism, it's goal of nirvana, via the possibilities of the human brain, and mental states.