Complex sentence: Initially he was part of the Disciples of Christ or Campbellite movement, he joined the early Mormon church, called the Church of Christ, in 1830 after their bishop, Sidney Rigdon also joined the church.
Split into simpler sentences: Initially he was part of the Disciples of Christ or Campbellite movement. He joined the early Mormon church, called the Church of Christ, in 1830 after his Campbellite bishop, Sidney Rigdon also joined the church.