I hate to put the blame on to any "one" reason for Southern Europe doing badly, but I came across an article that probably gave a better reason why there was so much difference between North and South Europe, and the theory it presents is religious difference between Protestantism and Catholicism. Protestant (read the bible) & Catholic (follow the pope). This gave the north literary rise, and literary history, and advanced them above their southern neighbors.

Corruption could be fallout of illiteracy, or maybe, lack of corruption could be a fallout of advancing literacy.