Catastrophic events often lead to the question of why. For most folks extreme misfortune, to utter overthrow or ruin, will cause such a question. To the philosopher a better questions may be "why not", or to the stoic "because", but to a bishop from North Africa it was "The City of God".
For over a thousand years Rome had been the ruler of the known world. When Alaric and his Goths sacked the city of Rome in 410 AD, the city that most felt would stand forever, lost most of its glory. Lots of folks wanted to know why.
Of course all sorts of reasons were given among the various groups looking for a scapegoat on which to blame the events. [Sound like today?] One such explanation was given to the Christian community by this fellow from Hippo. [Modern name of city is Bona.]
It is not an easy read! Written some three years after Rome first collapsed, it is a detailed analysis of the reason Rome fell. [Written from a particular point of view.] It is basically a theology of history from the point of view of the existing churches of the day. Thirteen years in the making, it was an attempt to explain Christianity versus the official religion of imperial Rome. It was to answer the question why as to the fall of the city of Rome.
My copy, published 1950 by Random House, is a translation by Marcus Dods, with an introduction by Thomas Merton. For those who have the guts to read this text will need to stick it out. Why? Why not?