Some of both. Most of the economics literature discusses German-style banking in terms of the efficiency of capital allocation versus capital markets and, therefore, has little on the causes of the German system. For example:
http://research.stlouisfed.org/publications/review/98/05/9805cf.pdf
For more history, here is the volume on German-style banking in a four volume work on the history of banking in different countries:
http://oll.libertyfund.org/?option=com_staticxt&staticfile=show.php%3Ftitle=2241&chapter=211367&layout=html&Itemid=27
