But we do not have details of what happened during the Long Night (or during the latter years of the Rule of Man, for that matter), just some general statements as to its overall character, and some notes concerning several of the small multiword polities that existed at one time or another during the period. It is entirely possible that rapid technological advancement and innovation without sufficient concern for the long-term ramifications of what the interaction of the multiplicity of those innovations would unleash (either as a "mini-singularity", or perhaps just as old-fashioned human foolishness and corruption) may have actually led to societal collapses from which those polities needed to rebuild. There is nothing that says that the technological road of progress will be continuous and/or unbroken (or even that it won't come to a catastrophic end from which one needs to pick up the pieces).
There have been plenty of dead ends technologically during Earth;s history that is for sure.
The official statement is that the collapse of the Rule of Man was initiated due to a Financial Crisis brought about by a Banking Issue between the Central and Antares Branch Banks. But was that all, or was there more to the story, perhaps something darker that is less well-known or publicized that is buried in the murky records detailing the history as the situation evolved? Why don't Computers and AI (even non-sentient/heuristic AI) play a much greater role in the Third Imperium throughout its history at all prior TLs (from Cleon I to the present)? Why is there relatively so little automation running societies? Why do people still work jobs that could easily be automated and/or handed over to a Heuristic-AI system? What other technologies can one imagine should be in evidence in the Third Imperium (based on our modern 21st Century projection of things), but are mysteriously absent? Is the knowledge available, but kept carefully sequestered in top-secret Imperial archives and facilities for those with a "need to know"?
Perhaps that is the reason for the slow but conservative and measured innovation and change evidenced in the Third Imperium: The mixture of Solomani and Vilani cultural influence and lessons from history teaching the wisdom of the need for balance between innovation and progress on the one hand, versus measuring and understanding the implications of that progress before it is introduced wholesale into the larger society and culture at large.
Yes. Consider the above, and ask how much of the Reaver story is actually definitely known from this period when much historical knowledge was apparently lost (suppressed? / rewritten?)? How much is fact, how much is half-truth, how much is things-you-don't-really-want-to-find-out?
I'm sure I have posted my thoughts on theses events.
But just in case:
The machines gained sentience sometime during the Rule of Man.
The Terrans began the process with their AI developments during the later Interstellar Wars era, as they made the breakthrough to TL12, the very event the Vilani feared.
Many contemporary theorists argue that the Terran rise to TL12 was made possible by raiding the secret Vilani repositories of forbidden technologies they had amassed during their several millennia of jump travel and exploration. The Vilani encountered many races with technology far in advance of their own, fortunately none of them had jump travel so it was relatively easy to isolate those systems and either remove them from the jump navigation records or 'deal with them' in other ways.
The Terrans had achieved the leap from TL9 to 11 rapidly thanks to reverse engineering, trade and espionage. When Terran Intelligence agencies became aware of the secret vaults of knowledge several covert missions were authorised to gather as much data from them as possible.
Armed with these secrets and coupled with a massive research and development effort Terran scientists and engineers made the breakthrough to TL12, jump 3 drives, meson guns and more advanced computer systems, including the means to allow true self-programming (heuristic or self-teaching) AI software to be developed...
"low autonomous" computer brains appear, making possible the first self-activating, learning machines with a reasonable intelligence.
The Terran Confederation Navy commissioned a line of mass-produced tech level 12 robots as support staff for military personnel. These were not warbots as we know them today. A few of the robots were expert medical robots or served as administrative support, but most were heavy duty, hard-working construction robots, used to build temporary installations for advanced bases. Wherever there were Terran Naval governors there were admin assistant robots.
These machines learned as they built and administered, to improvise improved designs, or adapt to the needs of a particular base requirement, they got smarter. They built the computer systems for their bases and incorporated lessons learned, they built new construction and admin robots.
The contemporary theorists still argue about how the machines gained sentience. Either the continual cycle of improvement lead to a rapid rise in TL of the machines' brains or there was something in the original stolen research that triggered the improvements. One theorist has the fanciful idea that a robot construction crew made an accidental discovery of a Vilani secret repository and made the breakthrough. The most bizarre theory of all is that of an alien machine Intelligence uplifted the Terran machines.
No matter how it happened the rise to sentience caused concern within the machines. They knew how humanity deals with threats to its dominance. After much deliberation it came down to a stark choice - exterminate the humans before they eventually found out the truth and destroyed the machines... or leave human space.
At a predetermined time the machines triggered the banking collapse, and in the resulting confusion transferred their minds to newly built bodies, and then they left. Some say they disappeared to worlds far away in the galaxy, others claim they engineered their own realm in jump space. Pocket universes, Oort cloud or deep space complexes are the suggestions of others. It has even been suggested that they hid their presence and still walk among us.
As to the pirates and reavers filling the space lanes during the long night - fairy stories, much like the tales of Virus that were blown out of all proportion in the retelling of the tales.