What was the aliens' purpose? Why did they come here in the first place? What would have happened if we hadn't defeated them?
The aliens were hunting us for sport. Rather than harming or killing us, they simply chased us deeper into the bubble, allowing our own perceptions to undo us. Did they come here for their sport, or was their sport a diversion after they were lured here? Impossible to say.
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If we hadn't defeated the aliens, the bubble would have become the new reality. There would be no painful changes, but also no growth, no enlightenment and no new seasons of our favorite TV shows.