Why was Jesus resurrection necessary? Didn't he already defeat our sins on the cross? Why does the resurrection prove that Christianity is true?
In the words of apostle Paul in 1 Corintians 15:17-19:
"And if Christ be not raised, your faith is vain; ye are yet in your sins. Then they also which are fallen asleep in Christ are perished. If in this life only we have hope in Christ, we are of all men most miserable."
Christianity is the only religion in the world that claims their leader resurrected from the dead. No other religion can claim that. And that is the ultimate test for the eternal power of a religion. Many teachers have been born on this planet and started new religions. But they all died like regular human beigns, and their religions died with them. Christianity's leader though rose from the dead and lives forever. That is why no force in the universe can stop this religion. It continues to be watched over and advanced by its leader.
If Christ did not rise, then how could we believe that He will raise us from the dead in the end of time? If He did not rise, then how could we believe His promises of eternal life for us?
Chrisitans have been and continue to be the most hated and persecuted group of people on Earth. If there was no resurrection, we would be the most miserable people ever. What would be the point of going through all the suffering for our religion if we just die and disintegrate? Why deny all the pleasures of this world and suffer for Christ if He was not alive? Millions of Christians have chosen to die for their beliefs with courage because they were confident that their leader lives and can raise them from the dead.