How about we say that the traveler or the Great Machine got destroy by the human race because a fallen ship or transmission came talking about the Great Machine bringing darkness. So we can say that either the traveler destroy the hole human race then made ghost to revive them and make a fake history that he die or a Person went to the ball destroy hem and he created a huge explosion leaving hes huge ball intact cause he knew that one day that might happen and created that ghost before that with commands to revive the strongest people he knew or saw to persuade them thinking that darkness ( Fallen, Hive ,Vex, exc.) created the collapse as we see in the history. The Vex are know what happens if they destroy the traveler cause they can go trow space time and create a simulation to know there next move. The Vex may of had created the Traveler sense we don't know if it is a person or a machine we can say that the Vex could of build the Traveler as a self conscious AI to exterminate those who did not accept the Vex ways or where in war for there materials or a especial thing. But the Traveler decided to just wonder off to destroy worlds making them feel like he is trust worthy, studying them how they do things to find there weakness and then strike. By either erasing there memories or just a full extermination of the planet. The Hive seem like creators that use magic as there main source so we can't say the Traveler came from them cause Oryx could of just Taken hem. But from what we seen Oryx might of been a captain who had normal life like humans until the traveler came to there planet to destroy it but we can't say if he did cause there are no evidence. The Fallen is really simple cause a lot of us know they suffer the same as us the human race but the Traveler seem to just leave the planet to die because the Fallen were not probably strong enough to destroy hem like the humans probably did.