Jeremiah is addressing the kings of Judah. "The Lord gave you the responsibility to take care of the people of Judah. But, you have done a poor job. You were supposed to take care of the flock, but you didn't. You were supposed to keep them together, and you let them get scattered."
God will not leave the sheep hungry and scattered. Jeremiah reports that the Lord will send them a new shepherd, one that will reign over them wisely and will bring justice and righteousness to the land.
Mark could see parallels with the situation of his people in his time with so long-ago ancestors who needed protection, and who had not been getting it from their religious leaders.
How is the church today living out this prophecy? How is your congregation?