The circumstances that led to the end of their species were neither unexpected nor especially traumatic. They were, after all, both a highly evolved and wondrously enlightened people.
They understood it was in the nature of all things to experience both a beginning and an end. They did not bemoan their fate. They accepted it with the stoic grace expected of those who truly understood themselves.
This is not to say they were either ambivalent or apathetic to their situation. They grieved, each in their own quiet way, but with no artificial pretense or excessive histrionics.
There is none to say which voice first spoke the words. That knowledge was not preserved for it, ultimately, was of no consequence. That the thoughts of one became the salvation of all is the salient point.
Why, that lone subject queried, must this be so? Why couldn’t their history, culture, arts and sciences, technologies and wonders be preserved inviolate for any and all to know of?
Their greatest minds turned themselves to the task, knowing full well nothing but success was an acceptable outcome. The entirety of their world had entrusted them with nothing less than their immortality. To fail was, simply, not an option. Succeed they did.
To all corners of space were launched the sleek crystalline craft, each one the repository of the priceless memories of a world. Their sole responsibility to ensure it would be known that it was so long ago, but the memories hadn't faded and never would.