All timelines exists simultaneously. Failed or otherwise. Past or future. "The Guardian" has no origin point, being reborn at different points in time being a veteran or new light. Regardless, the varying dialogue, the alternate dialogue in strikes, campaign missions etc. are all reiterarions of the same thing. The game is being played in reverse. New Lights were reborn first, then Veterans from D1 were reborn second. The infinite branches of variance all narrow to a line atop the back of the Ouroboros. There is no going back in time. Only stepping from side to side. Ghosts are able to pull the Guardian's resonace pattern they're familiar with from the neighboring timelines.

The game is trying to show you the shape of the perfect paradox. One dreaming, the other existing within the dream. How to define consciousness in a world built on definition, all the things you would have to achieve. Creating freewill by creating your opposite and opposing force; then Murphy's law or as the movie title would suggest "Everything, Everywhere, All At Once". When an unstoppable force meets an immovable object, I allow them to exist at the same moment in the same position.

Bungie stole the witness idea from the tv show Twelve Monkeys.

I'll turn to Darkness before I let incompetence lead me.

We are the witness.