Here Dante is waylaid for a time since darkness is upon the Mount of Purgatory. Dante sees many kings who failed in their lordship in various ways.
Every person longs for a good ruler, a good king, a good president, prime minister. History proves that no ruler was perfect. Not every decision was just. Not every person’s way of life just or entirely virtuous. Everyone is disappointed by a ruler or president even if you vote for them.
We long for justice and right ruling. Is there hope even for an unjust ruler? Of course.
In Esolen’s commentary he reminds the reader that the kings in Purgatory are in a valley doing what the did not spend enough time doing as rulers: praying.
Every president at least in some form, the emphasis if he is a Christian or believes in God or prays to God is always brought about. Why is this? Because in the Western world, even the Eastern it is believed that authority is given by God. That justice is given by God. (In fact all the cardinal virtues, and of course the theological virtues.) That a ruler has a great weight upon their shoulders and the only way a ruler is able to make the right decision is by the grace of God.
Even the virtuous kings make mistakes. But the great hope and consolation is that there is One perfect King who will enact perfect justice in the midst of human injustice and failing.
This is the subject of Canto 7 in Paradise.