Why did so many of the great thinkers of the Age of Enlightenment not question the reality of a deity?

The Age of Enlightenment is so named because humanity began to turn away from superstitions. belief in magic and acceptance of explanations based solely on their being traditions. They began to evaluate the mores and institutions of society critically. Rather than the supernatural, they looked to reason and the scientific method for explanations of what they observed around them.

Many turned away form traditional religions and to deism, but a very small number were willing to break entirely with the idea of a creator deity. Why do you think this might have been true?