You are really stretching it with your interpretation. That's not what Paul meant at all. Think about it. Paul, formally Saul, a Hebrew's Hebrew and stauch persecutor of the Christian church is converted within a short period of time subsequent to Jesus's cruxifiction and becomes one of Christianity's greatest pioneers and preachers. The disciples, in hiding for much of Jesus's trial, death and burial, begin to preach fervently about Christ within a short period of time after His death, which eventually led to 10 of 11 disciples being martyred. Within about a twenty year period after Jesus's death, the Christian church grew exponentially in Jeruselem and Rome, with many converts from Judaism. Paul explicity references the initial witnesses to Jesus's resurrection in I Corinthians, Chapter 15. This was not some made up rationalization. It would have been exposed for what it was if it were not true and would have had no lasting power, let alone it would not have survived the religious leaders who were vehemently opposed to it for exposing it as a fraud. But they didn't. And regarding your statement that Jesus failed to fulfill the messianic prophecy, He
First, the Christian church did not exist when Paul converted. What existed was a sect of Judaism. Paul was simply leading one form of the Jesus movement. That form was actually different from what Peter, a disciple of Jesus, was teaching. More so, it was also different from what the brother of Jesus was teaching.
Also, I would like to see some evidence for all of the disciples being martyred.
Finally, if you look at the history of Christianity, you will see that you simply are wrong. Christianity didn't really take off until the second century. During the first century, and during the time of Paul, it was still a Jewish movement. Paul himself was a Jew throughout his life.
Also, one can see the evolution of the idea of Jesus being resurrected. Paul doesn't even mention it until 2 decades after Jesus died. That is more than enough time for a myth to be created, especially a myth that was already so prevalent. That being that the general resurrection would soon occur. Paul, a person never witnessing the crucifixion, not knowing Jesus, would not have had a hard time claiming that Jesus (basically a nobody), was resurrected. It was not out of the realm of possibility.
Finally, by all accounts, Jesus was a failed Messiah. There really is no debating that.