Why did Christ have to die as a result of Adam's sin?

Les explains that Paul describes himself as carnal, a son of Adam, sold under the old Adamic nature or under sin, because the law is spiritual but humanity is fallen. When Adam fell and sinned, he plunged the whole human race into that condition, so Christ had to die to bring fallen mankind back to Himself. Les notes that some people become judgmental toward God, asking how God could call them sinners because of what Adam did 6,000 years ago. He says he cannot answer that, but God's mind and thoughts are higher than ours, and God sovereignly set it all in motion. God placed Adam and Eve in the garden and gave them one simple responsibility: not to eat of that one tree. It was a means of testing whether they would remain obedient; the fruit itself was not wicked. Adam failed totally and ate, and the sovereign God declared that now that Adam had sinned, all his offspring would inherit that sin nature.