They were simply willing to die rather than deny their own eyewitness knowledge of the resurrection of Jesus Christ -- hardly something for which a man would be willing to die if he knew he was lying.
Just as other people were willing to die rather than deny their own eyewitness knowledge of other "facts" that are incompatible with the "facts" that the Apostles were willing to die for. Your "proof" proves nothing. People believe all kinds of wild things they claim to have witnessed, and many of them will die for these. It's just normal human psychology at work.