Christian commentators commonly understand Joseph's words as an illustration of divine providence. His brothers acted freely and wickedly, and they remained responsible for their betrayal. Yet God worked through the circumstances to preserve Joseph, his family, and many others during a devastating famine.
This does not mean that God approved of the brothers' cruelty. Their intentions were evil. Rather, God was able to accomplish a good purpose despite their wrongdoing.
Some Christian theologians emphasize that God sovereignly governs history, even when human beings act with sinful intentions. Others stress that God can redeem the consequences of evil without being its moral author. Both approaches recognize that the Lord's purposes cannot ultimately be defeated by human wickedness.
Christians also see a connection with the death of Jesus. Those responsible for His crucifixion acted unjustly, yet God brought salvation through the very event they intended for destruction.