I believe the background of Pioneer 1 and two separate themselves enough to describe that. Pioneer 2 and 1 were shipped out as ancient scouts for worlds. Ragol itself was among the worlds scouted for Pioneer 1 and habitation was sent out with Pioneer two behind with the wave. Pioneer 1 was deconstructed and used as construction material for the colony and Pioneer 2 orbited Ragol during PSO's events. I feel that the photoners, those who visited Xion, were part of another Pioneer ship (we'll say 3 for the sake of caution ) and that contribute to the growth of this Oracle Fleet.
Pioneer 3 is probably what was upgraded into the Oracle Mothership and allowed it to salvage the remaining part of the civilization that the Pioneer ships were meant to save. Given Luther's standing, it suggests the photoners may be equivalent. It would fall in line with the technology on Pioneer 1 and 2 as well as Xion being the progress catalyst for what we use today. Spoilers Dark Falz out of PSO2 derive their power. The Profound Darkness is a clone of Xion.
One little hitch with this particular theory. We all know what happened to the civilization that is first in PSO. Wherein we learn that at some point they created an AI to restore Coral's environment. Those paying attention will remember that D-Cells, were the reason behind the Pioneer job in the first location. D-Cells had forced it into Coral, via an asteroid or any such macguffin, along with the authorities wanted to weaponize it.
They put together the Pioneer job to track down the original source of this D-Cells, and found Ragol. Going back to the first point, PS0 happens 100 years after culture gets nuked. For anybody who doesn't know already, Pioneer 2 flipped Coral the bird at the end of Episode III and colonized Ragol after the complete and total destruction of Dark Falz and Olga Flow following their duel to the death. Which is just another narrative point that runs against PSO2.
I will go through the rest of PSO2 narrative between what is left of Episode 2 and Episode 3. 1 final thing is the fact that it is possible... they THOUGHT he had been ruined. If that is the case, it might lead to being the evidence that contributes to the understanding that Dark Falz can't be destroyed. This knowledge of the immunity to complete destruction is immutable. Therefore any Dark Falz being destroyed does not follow the exact same logic as exhibited in PSO2.
More information about PSO2 in pso2ah.com