In effect, mayors and lesser nobles had a common interest: "the mayor of the palace was able to keep the monarchy in tutelage because of the support he received from the 'nobles', while they owed their whole livelihood to him." What is being spoken of here is vassalage and the elements of a feudal relationship in a localized world. An aspiring noble would do well to 'commend' himself as a vassal to a more powerful man, and the latter would gain more support for his expansionist agenda, just as the former would be raised in status with his master. Often, ascent took the form of being awarded an amount of property by the lord, which the vassal held as a tenant, conditional upon performing some usually military service. In the eighth century, such land was called a benefice. This dynamic was integral to the roots of the Carolingian dynasty as represented by Pepin. The Carolingians rose due to accumulation of noble support; the Carolingians in turn consulted the nobles before taking action. Thus something approaching a common, 'public interest' could evolve, and only from this period do we see local level leaders caring somewhat more about rural order and security than had the Merovingian kings.
Throughout it all, the Church remained especially important. During the most severe periods of civil unrest, bishops and priests would provide administrative continuity, charity, and even security. Something of a parallel administration, each city had a bishop. Often from the late-Roman senatorial families, their level of culture and civic mindedness was somewhat elevated. Further, rising men--such as Pepin's family--would often ally themselves with the Church, thereby increasing their legitimacy, as well as basis of support. There was another side to it, however. It was increasingly difficult for clergy so closely interacting with secular powers to maintain autonomy, just as the Frankification of the provincial episcopate degraded the quality and discipline of the clergy.