It seems to me that in this somewhat enigmatic letter, Gregory tackles specifically the phenomenon of installing in the particularly affluent and important monastic foundations (such as those in the imperial city of Ravenna) people lacking any monastic experience and, even more importantly, the will to follow the monastic creed. Richly endowed monasteries attracted clerics and laymen alike, as joining such institutions conferred both wealth and prestige. The letter suggests that even the abbots were chosen among the people from outside of the community, especially clerics, who – to Gregory's horror – continued to perform their usual ecclesiastical duties even after the abbatial ordination. It is my impression judging by the tone of this epistle that in the case of Ravenna the bishop was likely directly involved in the practice so revolting to Gregory. Bishop John could, for instance, reward those loyal to him with an abbatial office. The process of being installed as an abbot or a monk could be thus perceived as a political action rather than the matter of faith or ascetic calling.
It must be stressed that Gregory is here in no way against clerics heeding the monastic vocation or monks taking the holy orders in general. However, he is definite that the same person cannot perform the clerical duties outside the monastery ("in the world", so to speak) and, at the same time, guard the proper observance of the monastic discipline. The discipline which obviously obliged all monks to fervently avoid any contact with the outside world.