As a former slave, Paul was the first person to make the slave punishment, crucifixion, respectable in Christianity.
When James and Peter were crucified in 46 AD, the oral tradition altered the means of death into beheading (with the sword): Acts 12:2. In the case of Jesus, too, the oldest sources only refer to his execution, not to crucifixion: Acts 7:52.
Elymas/Paul was previously a Jewish Christian (Bar-Jesus = son, i.e. follower of Jesus). He was converted to Peter’s Christianity by Barnabas.