Intelligent people believe in "god", for the same reasons atheists follow scientific theories. Really, this first statement of mine is false, as it generalizes and assumes that *all* god believers and atheists are a certain way.
There are always exceptions to the rule, however, god believers and atheists are not so different from each other when seen from a broader perspective. While science has been crucial in bringing Truth to the world, there are still major constraints as to what we are able to perceive with scientific instruments. There are still theories that are followed by the scientific community.
Theories are also followed by the religious community.
You cannot get away from theories, whether scientific or otherwise. Theories/assumptions are needed to function in the everyday framework of "consensus" reality. You simply will not know all the answers to everything.
Then, there's the issue with language, semantics and definitions. A concept like "God" is so broad and subjective that the point is moot in trying to define it. The idea itself is too large for any humans to wrap their mind around. Then again, so is the astronomical distance from the earth to the sun, which the Christian religion is based on. (Sunday morning worship).
Scientists have long understood and discovered that beyond the light reaching us from the farthest reaches of the universe, beyond our observable universe time and space are subjective. Subjective like intelligent people's "God" experiences.In fact, the bible was originally called "Helios Biblio" - the book of the Sun.