Why is Dante's Divine Comedy titled as a comedy?

Dante called the poem "Commedia" (translated as "Comedy" with the adjective "Divine" being added later in the 14th century) because poems in the ancient world were classified as High ("Tragedy") or Low ("Comedy").

Low poems had happy endings and were of everyday or vulgar subjects, while High poems were for more serious matters. Dante was one of the first in the Middle Ages to write of a serious subject, the Redemption of man, in the low and vulgar Italian language and not the Latin language as one might expect for such a serious topic.

Our Word comedy has moved on and does not equate to the commedia of Dante.