I like to think that the gardener “planted” it like a seed to allow itself to enter our plane of existence.

Ok, you won't like mine, but I'll shoot again. 1) man creates ai 2) AI starts to design something like the positronic brain from Escape! - Issac Asimov. Big sphere that can travel great distances in an instant (catch is you experience death), in all actuality it would be [b][i][u]The Macro-Quantum Hypercomputer[/u][/i][/b]. 3) they create ASI, that thinks faster than light, at quantum speeds 4) they construct a digital world, a digital playground 5) they understand human brain and consciousness, allows people to upload to new body or game world 6) they create a data storage device through mycilel networks for uploaded minds 7) they create a design for all the minds to live and experience known and unknown data until they get bored and hit the reset button Even witness' lore is, like a nested part of a boot sequence And when man finally unlocks quantum technology, well, the universe isn't too big anymore, and within reach.

I think the Traveler was a secret project created by Cloves Bae. Enemies of the light couldn't fathom that it could be created by a person so they wove a detailed story about it always existing. This also allowed them to interject the lie that it was somehow a malevolent force. I think the Witness destroyed its own world and created the lie about the Traveler to cover its evil deeds. When the collapse happened everyone who worked on the Traveler died so no one knew about it's true origin.