Jesus did not come simply to die for sinners but to testify to the truth of God (John 18:37). His death is the result of what he said and did, proclaiming God's rule, not Caesar's or any human master's. In other words, his "dangerous" teaching and act cost him a life.
In 2 Cor 13:4, Paul also admits the fact that Jesus was crucified "by or from weakness" (eks astheneias). That is, he insinuates that Jesus could not overcome Roman violence because he had to continue preaching God's kingdom against Rome. But the crucifixion is not the end of the story about Jesus. Paul says without a stop in the same verse: "But [Jesus] lives by the power of God."
Given the above view of Jesus, Paul's central message is that Christians have to imitate Christ in his faith and spirit. They must be led by the Spirit, submitting to the law of God. They must die with Christ and live to God. Christians (followers of Messiah Jesus) are not mere believers of Jesus or beneficiaries of him but followers of his life and faith. This implies that they are not welcomed by the enemies of God's justice, running the risk of losing their lives because of their testimony to God. But they should not give up on the work of God because God is their true hope.
