In Benedictine abbeys abbots were responsible for the running of an abbey and its material wellbeing as well as the spiritual health of the monks in their charge. They were lords of the manor, so important on a local political and social level as well as often being prominent figures in secular government. They were also patrons of art and architecture.
Abbots were selected from within the abbey. The result had to be confirmed by an ecclesiastical superior and, under the terms of many charters, by the patron. During the reign of William Rufus this was problem as he kept a number of posts vacant in order to draw the income from the land, based on the principle that when the land was vacant of its tenant ( a role fulfilled by the post of abbot) that the Crown, which was the owner, took the profit. And clearly elections were not always as straight forward as the basic description suggests. There were all sorts of internal and external political shenanigans that didn’t necessarily have a great deal to do with piety.
Originally the abbot filled the role of father figure but as time passed many abbots were taken to task for not eating in the refectory with the rest of the monks or living away from the cloister. As well as not having oversight of the monastic foundation which they were supposed to be running they were also effectively invisible in terms of the example they were supposed to be setting. And if they were present the example was not necessarily positive – one of the abbots of Selby was taken to task for being drunk most of the time and for womanising.
As the medieval period progressed abbots were celebrated not for their piety but for their administrative capacities and control of the finances. This in its turn led to some interesting, not to mention creative, accounting in terms of pasturing their sheep on common land or pocketing the proceeds for themselves rather than the chapter.
Heale, Martin. (2016) The Abbots and Priors of Late Medieval and Reformation England Oxford: Oxford University Press