we are forced to enter into a race against an usurper who aspires to the godhood we were unaware was within our grasp. emphasis mine
we become a truly intergalactic civilization once more, in full command of the relics our progenitors left behind.
This is where our interpretation fundamentally differ. You interped the events of Homeworld 2 - esspecially the chase after Maakan - as a test and frame the acquisition of Sajuuk and the Core Trinity as something that was meant to be.
I disagree with that reading. And here is why:
Exhibit A: The Hyperspace Cores
1. "In the first time, the Great Hyperspace Core was found..."
2. "... the Second Core was discovered on a desert planet..."
3. "This is the story of the End Times. We know this because Third Core has been found."
The Hyperspace Cores were found
. They were not gifts or heirlooms handed down from the Progenitors to worthy successors, younger species happened upon them and used them.
There is only a single indication that some kind of line of tradition for the Hyperspace Cores was ever intended and that during the mission after you have acquired the Oracle and it leads you to the first Progenitor wreckage. This then however immideatly contradicted in the post mission cutscene...
... which describes the behavior of the Oracle akin to failsafe.
Exhibit B: The Progenitors are unrelated to the current species
(I assume it speaks for itself)
Okay it doesn't.
This is the definite feature of the Progenitor other than that their technology survived them. There is no mention of any futher connection the galaxy other that they arrived and stayed until their civilisation came to an end. There is no mention of them contacting any species now in existence directly.
While the Prophecy exists (see below), there is no mention that it was inspired by the acutal Progentiors. It might as well have been created through contact with what was left behind by them (which would also explain why the Oracle -implied to be part of the Progentior ship's bridge system- is so far away from it).
Exhibit C: Sajuuk and the Prophecy
All knowledge about Sajuuk before finding the actual ship, is presented in the from of prophecy and open to interpretation. The following bit is esspecially interesting:
Now the dictionary definition of "to unleash" is "to suddenly let a strong force, emotion, etc be felt or have effect", considering what is revealed in the Epilogue is the purpose of Sajuuk (to open the intergalactic hypersacpe gates) that is clearly a powerful, positive force taking effect.
However, you also leash out of control animals and considering we have no information on how the Progentior civilisation ended (the Progentior ship is said to have broken apart but there is no cause given), it might be that closing down the intergalactic gates and hiding away the key to it, may have been preventive measure.
As this is information handed down through ages and languages, it is notoriously unreliable and doesn't give credibility to either reading.
Exhibit D: The Chosen One
There is of course the matter of "the Chosen One":
But it is never quite clear, if this means something positive or negative. Actually the Epilogue goes so far, in my reading, to suggest that what the Chosen One might not have a set purpose but instead who the Chosen One would be would determine their effect. This is cooberated by the emphasis on Maakan's "shadow" in the intro":
Due to unclear line of tradition of the prophecy it is also not beyond imagining that this part was added or distorted.
Exhibits A and B combined make clear that by definition Maakan cannot be an usurper as there is no rightful claim to any of the three Cores. They, Sajuuk and the hyperspace gates are not an inheritance passed down but remains (i.e. objects that survived the span of time but originally not meant to - as opposed to tradition) that both Maakan and the Hiigaran freely use.
While said use eventually has a positive impact, there is no indication whetever or not it was intented; acutally the Intro and the Epilogue contradict that reading by highlighting that it is the person that fills the role of Chosen One determines the kind of impact the Trinity has.