What explanation does her father give her for how their king got his position?

Her father then tells her the story of how the King came to power. He tells her that Reza Shah, the father of the current King, had been a soldier who had helped organize an army to overthrow the Emperor of Persia and install a republic. Her father’s history is a flashback to Reza Shah’s rise to power: Reza Shah and his conspirators sit around a campfire and plot their attack. Reza declares, “If it is God’s will, we will reach the capital in 19 days.” One of his co-conspirators thinks, “And even if [God] isn’t, what can stop us?”

He tells her that the British had learned of Reza Shah’s desire to overthrow the Persian emperor and had decided, because of Persia’s great wealth of oil, that they would help him. They had approached Reza and told him that he could be Emperor, a political situation that would be much better for him personally.