Intentional war, an apocalypse followed by Technology Dependency failure.
We went through a nuclear race and MAD [Mutually Assured Destruction] policies, and there remains enough nuclear weapons to wipe out humanity. But you don't have to do nuclear war, per se, I'm just using that idea as an analogy.
Don't make the mistake of thinking a very advanced civilization is automatically accompanied by benign politics, or that they have stopped grasping for power, or have different parties with different ideas on how to rule, to tax, to provide their citizens freedom.
Peace is not brought by technology, as a glance at the world today should show. If anything, it can cause contention FOR the technology: people are fighting over access to expensive forms of health care and medicine that did not exist two centuries ago, but now that technology has delivered this semi-magic, people are fighting hard about how much profit we should allow to be made from it, and even without profits, who should pay for it.
Despite high technology, your civilization can have wild fights over similar advances. Who gets to be immortal, and who has to die? Why? What does the civilization owe individual members of it? Who is being (or feels they are being) exploited for others that live wonderful lives in leisure?
Find something for them to have political fights over. Religion, money, whatever.
WE are a pretty high-tech world, and are still arguing over these things. Devise a high tech world where bitter fights over religion are still rampant. And even if they reject religion, atheists like me (only 7% of the world) can still disagree vehemently over philosophical questions, like how much (if anything) we owe to society or our fellow humans, or fellow life in general, and in what form. These beliefs can range from supreme selfishness to complete devotion (to others, not God).
Then some group on the losing side, perhaps denied technology that would save their lives, decides if they lose, everybody loses, and they intentionally engineer the death and destruction of their opposition. Their plan to use war to get their way partially succeeds, but, people being people (whether aliens or not), their opposition had their own fanatics, and had used high-tech to engineer a dead-man switch. That kicks in and wipes out their opposition. Nobody wins.
Then the scattered remnants write your history, but like any high-tech civilization (including our own), they have become life-dependent on their technology which they do not fully understand, and that is not functioning after the war, and the people that could fix it are dead. They grow old and die, unable to either diagnose or cure diseases or make medicines. What % of people on Earth knows how to create a simple antibiotic, or any other medicine?
Destroy the energy and/or manufacturing base, and everybody dependent upon manufactured medicine dies when it runs out. Living spaces that depend on machinery to cool it, warm it, light it, provide oxygen and air pressure, become at least unlivable, and perhaps death traps. Sanitation and water that depend on energy for pumping and cleaning all stop, filling the streets (or something equivalent) with sewage.
The food supply, naturally segregated (like our own) into production districts (huge farms or space platforms) because sufficient power allows remote production and transportation to the consumers, also fails. Without power, the food production itself fails, uncared for, and the transport mechanisms all fail too. The population enters a phase of starvation.
The population is returned to our middle-ages or dark-ages. But it is worse: People born into that situation do not survive to adulthood without strong immune systems, and from infancy their body and mind adapts with muscle and learning to survive in a world of shortages and wants. A modern couch potato dropped into this situation just dies. Thanks to medicine, the weak immune systems and those with disabilities were not culled in childhood, and the adults are unfit, because they have not spent lives filled with physical activity, walking 20 miles a day, hunting, gathering, grinding grain, preparing food and making weapons from scratch. Like most of us in the real-life modern world, they literally don't have the muscle to survive, and even if the young do, they haven't spent a lifetime learning and practicing the skill set to survive in a world without power and technology.
Say they are unable to reproduce naturally or keep their children alive without robotic assistance and assistants, and are barely able to communicate in person. Their food may be completely processed, and the machines don't do that anymore. There is likely no "wild" area for them at all. There may be no animal or vegetable food sources for them to find anywhere, their whole environment is a machine run habitat.
Religion and politics are their apocalypse, and due to their extreme technology dependency, within a few generations post-apocalypse, they go extinct. But before the apocalypse, a few saw where they were going, and wrote about it. And during the apocalypse, before the last machines failed, they wrote about what had come to pass. And that was what was left to posterity.