Many people die for causes they believe are true, even if they are mistaken. But the disciples were different—they claimed to be eyewitnesses of the resurrection. If it was a lie, they would have known it.
Almost all of the apostles faced persecution, and many were killed for their faith. Tradition says Peter was crucified, Paul was executed, and others suffered greatly. Yet none of them denied their testimony.
If they had made up the resurrection, surely at least one would have confessed under pressure. But they held firm, even to death. This shows they truly believed what they saw.
Of course, dying for a belief does not make it true, but it proves sincerity. The disciples were not lying or inventing stories. They were convinced Jesus had risen.
Their courage inspired others, and the church grew even under persecution. The willingness of the apostles to die for their message is strong evidence that it was real.