Jesus learned obedience by the things He suffered and how Job endured his suffering - trusting God without an explanation of why. And, how after his test he was restored but with a new understanding of who God is. Suffering is part of the curse of sin and also a means for accomplishing the purposes of God.
The "why" may never be known in this life unless it serves God's purpose to reveal it. Our part is to love, trust and obey. "Why" because He is God - who knows All things.