Jesus "was made sin for us", not a sinner for us. No sinner can redeem other sinners, what himself. But only God, and Jesus was God, God who created us, has or IS the Power to let Himself be "made sin for us" to OBLITERATE OUR SIN IN HIMSELF, because He not only has "Power to lay down My Life", but even more, "Power to take up My Life" and "IN HIM", our life "TOGETHER WITH CHRIST".
For no moment became Jesus Christ a sinner, the actor of sin, for that moment alone would have been the repetition of Adam and Eve's FATAL MOMENT. But Jesus became the Subjected under sin, under our sin, which was placed BY US "upon Him" and "made, Him, sin for us", for "us" who ACTED the sin so that GOD The Righteous could declare "US", the "sinners", the murderers of GOD, righteous.