What led Dante to write The Divine Comedy?

Dante says in the opening that he is, at age 35, at the midpoint in his life: he is halfway through his 70-year path in life. Yet, he feels lost in the woods. He cannot seem to find the "straight path" to salvation, and he feels assaulted by wild beasts. In the fictional world Dante creates to try to explain his inner struggles, Virgil finally saves him. Through their imagined journey to the underworld, purgatory, and paradise, Dante finds his way again. He writes The Divine Comedy to show others the consequences of sin, which he describes in very vivid terms, and to reveal how to achieve paradise. His struggle for the right path becomes ours, and we benefit from his metaphoric journey from darkness to light.
Dante also wrote The Divine Comedy because he was living in exile. He had been part of a political group, the white Guelphs, who were defeated in Florence in the very early 1300s. Exile gave him time to write, and the long poem was also a way, at least in literature, to settle scores with his enemies, who are imagined to be suffering in hell for their misdeeds.