Sadly, some pastors leave because of a hireling mentality. They leave their churches precisely because there are problems. When the wolf comes and tears into the sheep, they find it uncomfortable to be there and they move on. I don't say this is always the case, but it may be true more often than we like to think. It appears that they wish to turn the church over to the wolves who are at first only nipping at them. They run because they are hirelings who do not love the sheep.
Jim Elliff