I would say there are many societal changes which did that, but here are some of them: the growth of the publishing industry, increased literacy rates in the middle class, the greater amount of leisure available to people.
18th century is distinctive with many important historical events, among them Industrial Revolution and French Revolution. But there are literal characteristics which gave rise to the novel-writing and the rise of the literature. During the 18th century book publishing business started taking a rise. Education became important and the middle class started making its place in society. Geographical explorations and travelling started shaping people's leisure.
