It took a complete reversal of human thought. God had given Joseph a new way of viewing life, it may have come through experience, or it was simply a gift from a loving Father. Joseph was different, Israel knew it from the very beginning and so did his brothers. There may have been many justifiable reasons for Joseph’s brothers to hate him, but I believe it all came down to him being set apart from them. God had a purpose for Joseph that He would see through to the benefit of all of Israel’s family. It was probably not until much later in life that Joseph recognized what was unfolding even in all his suffering, but in a beautiful moment of peace He accepted/delighted in it. I think Jospeh’s forgiveness reflects and even greater humility and deep love he had for people. God’s goodness towards Joseph had less to do with his earthly circumstances (having or not having), it had more to do with how Joseph fit into the story of God and His people. God was using Joseph to bless others and that was enough to warrant forgiveness and even joy.
These comments are my opinion of course and could change at any moment 🙂