Why did Daniel Defoe wrote his Journal of the Plague?

Daniel Defoe wrote "A Journal of the Plague Year" as a work of fiction in 1722, describing the Great Plague of 1665. He used the novel to explore themes of human behavior in times of crisis and to provide a vivid account of the devastation caused by the plague in London. Defoe's goal was to reflect on the impact of such an event on society and individuals.