Why is the Zelda timeline split?

Why is the Zelda timeline split? The Split Timeline concept states that after the ending of Ocarina of Time, the Zelda timeline separated in two timelines thanks to Zelda sending Link back in time to relive his childhood. The two separate timelines have been designated by fans of the series as the Adult Timeline and the Child Timeline respectively.

The Split Timeline concept states that after the ending of Ocarina of Time, the Zelda timeline separated in two timelines thanks to Zelda sending Link back in time to relive his childhood. The two separate timelines have been designated by fans of the series as the Adult Timeline and the Child Timeline respectively.