Isaiah 53:4 Surely He has borne our griefs
And carried our sorrows;
Yet we esteemed Him stricken,
Smitten by God, and afflicted.
5 But He was wounded for our transgressions,
He was bruised for our iniquities;
The chastisement for our peace was upon Him,
And by His stripes we are healed.
6 All we like sheep have gone astray;
We have turned, every one, to his own way;
And the Lord has laid on Him the iniquity of us all.
Rom 1:18 For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men
God's wrath is revealed from heaven, not merely through the works of Satan. Since our iniquity was lain on Jesus therefore God's wrath was revealed from heaven and laid on Jesus.
That is something that makes a lot of people very emotional, including Christians :
"How could the Father punish Jesus who was innocent and who had not done anything"
That's because Jesus made the choice to take our sins upon himself so that we would go free
"But couldn't the Father have let Satan have a go at him while looking the other way"
Since the Father forsook Jesus based on our sins that were lain upon him, Satan had the opportunity to go after him but that was not sufficient for salvation. Jesus had to suffer God's wrath over our sins so that that wrath would be satisfied and would no longer be directed at us.
"But that makes God an unjust monster"
Jesus might think so but he didn't, he decided to obey his Father and take the punishment for our sins upon himself, including the wrath of God that was revealed from heaven.
"Okay but God shouldn't punish Jesus too much or let him endure too much suffering. After all, he was his own son and he was innocent"
You see, that is not for you to dictate, however emotional you feel about it.