In the early chapters of Acts all the Christians were Jews, that was until (1) Peter went to the God-fearing Roman Centurion Cornelius, and (2) some of the Jewish Christians who had fled Jerusalem, at the havoc wreaked by Saul, later started evangelizing the Greek speaking pagan Gentiles in Antioch in Syria. One of these was Titus, who accompanied Paul and Barnabas with their gift for famine relief to Jerusalem and then had a meeting with Peter, James and John.
However, throughout the period of time covered by the Acts of the Apostles, all the leaders, all the teachers, all the evangelists were Jews: there was not one Gentile among them … that was until Paul completed his two year house arrest in Rome, went to Crete and left Titus in charge of that island. Why Titus?