God presented him as a sacrifice of atonement, through faith in his blood. He did this to demonstrate his justice, because in his forbearance he had left the sins committed beforehand unpunished
One of the many things i love about reading the Bible slowly, and in order is that is shapes our categories and creates our concepts. If you asked many, perhaps even most, evangelicals, why Jesus died on the cross, the answers would probably range from 'because He loved me' to 'so i can have a personal relationship with Him' to 'so i can go to Heaven.' Hopefully some would say 'so that i can worship Him'.
Now all those answers are true enough, and glorious, especially the last one, which is far closer to the grand, ultimate, Biblical answer than the other three. Few people, myself normally included would say that the reason Jesus died on the cross was to answer the greatest problem in the Old Testament. Few would say to demonstrate His righteousness first and foremost.
The biggest problem in the Old Testament is 'how can God be good, and just, and yet simply put away the sins of His people. Sure there was the exile, but what about after that? Is civil war and a kingdom split enough to punish the adultery of David?' I mean, most people would say it in a better fashion than that, but you know what i mean. God the Father sent His Son to die to demonstrate the righteousness of God. This is why Jesus was laying down His life to show the world that He loved His Father, not us. Not primarily.
This gives such tremendous freedom in Christian counselling and discipleship. It means that when a student comes to me and says 'i am a terrible person,' i can say, lovingly and Biblically, 'yes you are a terrible person. And so am i. Welcome to the Gospel.' Christians need this Gospel! There is little to no freedom in the 'i'm so lovely Christ just couldn't help but die for me Gospel.' It doesn't work, it is not true.
The Bible is so radically, dangerously, consistently, persistently God centered that it ends up reshaping our categories, it ends up creating our concepts of what happened at Calvary. Can you imagine the impact if Christians read it, and took it seriously, and acted upon it?