Complex sentence: One possible construction of the "internal evidence" states that the Beloved Disciple wrote an account of the life of Jesus but that this disciple died unexpectedly, necessitating that a revised gospel be written.
Split into simpler sentences: One possible construction of the "internal evidence" states that the Beloved Disciple wrote an account of the life of Jesus. However, this disciple died unexpectedly, necessitating that a revised gospel be written.