In order for the Resurrection of Jesus to be a late legend, the story would have to be both late and a legend. It is neither. It’s a lot harder to lie about something when people are still alive to expose the deception. The accounts of the Resurrection were written while people who would have known better could still fact-check them. Despite this truth, the earliest New Testament documents include the Resurrection story, and the record of the early Church fathers demonstrates that the account was not altered over time.
For the Lord Himself will descend from heaven with a shout, with the voice of the archangel and with the trumpet of God, and the dead in Christ will rise first. Then we who are alive and remain will be caught up together with them in the clouds to meet the Lord in the air, and so we shall always be with the Lord. Therefore comfort one another with these words.
1 Thessalonians 4:16-18 NASB
But now Christ has been raised from the dead, the first fruits of those who are asleep. For since by a man came death, by a man also came the resurrection of the dead. For as in Adam all die, so also in Christ all will be made alive. But each in his own order: Christ the first fruits, after that those who are Christ’s at His coming, then comes the end, when He hands over the kingdom to the God and Father, when He has abolished all rule and all authority and power.
1 Corinthians 15:20-24 NASB