Answer:
Jeus knew who He was and where He was going -back to the glory He had with the Father 'before the world existed'.
Jesus vision for His disciples was that they would be witnesses to Him, to every nation on the earth. This began on the day of Pentecost when the Holy Spirit came and 3000 were saved as a result of Peter's preaching. Many of these were from different nations and so Christianity thus spread to other countries very early.