In Purgatory, what obsessions drive the Old Man to return with the Boy to the ruined house?

The Old Man in the drama Purgatory, by William Butler Yeats, brings his son in an attempt to save his own mother from the cycle of purgatory she has been stuck in since she died giving birth to the Old Man. On the surface, the Old Man is obsessed with his visions of the most memorable moments from his childhood. It becomes clear to the reader that these “visions” are really just painful memories from the Old Man’s childhood, and the Old Man is obsessed with the thought of expelling them from his thoughts forever.
The story is centered around a conversation that transpires between the Old Man and his son, referred to in the story as “the Boy,” whom he has brought with him to the burned-down house. The Old Man’s own son can’t see the “visions” and becomes increasingly angry with his father. The Old Man continues and tells his son what he sees:
His mother married a man whom others in society considered of low class, as this man did not have the financial stature that the Old Man’s mother did. The Old Man blames his mother for marrying too quickly and consequently leaving him to grow up with such a horrible man.
After his mother died giving birth to him, the Old Man’s father squandered the family’s wealth, became an abusive alcoholic, and forbade his son (the Old Man) to receive an education. We learn that the Old Man had to learn to read from the gamekeeper’s wife, and it becomes clear that he grew up in a very lonely, traumatic household. Eventually he burns down his childhood home with his father in it, appearing to feel guilty. The Boy, however, feels no sympathy and only resents for his father, who couldn’t seem to appreciate the luxurious life he lived.
The Boy resembles his grandfather, eventually driving the Old Man over the edge. Misplacing his hate for his father, the Old Man murders his son. He explains to his mother’s ghost that she is released from purgatory, but ultimately the cycle repeats itself and the Old Man continues to see the visions. This shows readers that the Old Man wasn’t really obsessed with releasing his mother from purgatory but with releasing himself from being stuck in the cycle of pain, resentment, and regret.