As a counterpoint on that, consider the reliability of memory. If someone is 10 million years old but can only remember the last 1 million except for vague impressions, , then couldn't something that happens 10 million years ago still be a legend?
Counter-counter point- even if that was true you still have guys like Alpha Trion just... around... in the modern era. That was one of my big annoyances with IDW1's treatment of the mythological past on Cybertron. Not only was it not really that long ago comparatively speaking but also Alpha Trion is one of your civilization's founders and he's still around and lucid. How is there any ambiguity to legends and myth???
Like if we had a dude alive and well and we could confirm beyond a shadow of a doubt that he was the Biblical Abraham then I'd like to think we'd collectively go "hey man we have some questions we'd like cleared up."
But this kind of stuff again happens when people apply the pop culture view of human history- static with no real understanding of timescales- to fiction about robots who live millions upon millions of years.
We're all assuming that all the Transformers remember everythign perfectly, and that they have records backing it up. Theyr'e robots so that is a fair assumption.
That's my assumption, I'm afraid. Look, human memory is fallible. And highly subjective to misremembering, false memories, and just good ole' bias. Ironically if this were Go-Bots all of this would make more sense since despite being mostly robotic their brains are organic.
But alas we're dealing with Transformers who have, as far as I know, fully synthetic and robotic brains.
So we have to deal with the reality that machines are capable of storing FAR more information, and doing so perfectly. Not tainted by bias, or a misremembered detail. When you record a video on your phone, your phone doesn't later change it to reflect its mood.
Given that we're dealing with machines I don't think "everyone just forgot" is a satisfying answer.
IDW1 tried to answer this with
"information creep," which is basically what you're describing. Technical errors, lost or corrupted memory files, etc.
My issue here is that this was basically introduced to cover for their own internal continuity issues? How does Nova Prime's era both fit the semi-mythological past yet also be recent enough that people from then are still around? Information creep! That's me reading into authorial intent, which maybe isn't fair, but it's how I see the concept. I'm sorry.
It seems likely that while some technological degradation would occur with some- maybe those who didn't undergo upgrades or who experienced damage that caused memory lose- the large scale cultural amnesia that would have to happen just doesn't seem possible to me with a race of machines and the multiple ways machines have of recording history in as objective a way as possible.
Throw in massive wars wiping out records(which we have a great example of in the G1 bots not having records of the Quintessons anymore when they show back up) and you can definitely have legends and myths that happened within the lifetime of living Cybertronians
I'm not so sure. We can only confirm the story of the Seven Sisters of the Pleiades Star Cluster- that there are six sisters but one was driven away- because we are able to roll back the star charts and see that 100,000 years ago the star cluster had seven stars but over time one drifted so close to another that they became indistinguishable from the naked eye. That's an endlessly fascinating look into a bit of primordial human storytelling and mythology we were only able to confirm because we literally rewound the sky. There is no one alive from that era, no written records, nothing but scant artifacts and a story we had to look up and back to even confirm it actually was that old.
So the idea of events that occurred within the lifetime of Cybertronians currently living being the realm of myth and legend just... doesn't sit right.
Like King Arthur- ok. King Arthur was far more recent than the Seven Sisters. IF King Arthur were real the earliest stories about him place him in the 5th or 6th centuries CE. Why don't we have proof of him if he's relatively recent? Well because Britain used to be part of the Roman Empire and when the Western Roman Empire collapsed society collapsed along with it and so Arthur was active during a time when, due to a series of societal collapses and wars, literacy and writing was at an all-time low. We have no contemporary sources of Arthur because if he was a real person there would have been very few people around to actually write his stuff down in his lifetime due to said wars and societal collapse.
But here's the thing... robots don't forget how to read. Take a human who grows up in the chaos of post-Roman Western Europe where the infrastructure and social systems his grandparents enjoyed are just simply gone and that human may go his entire life never learning to read and write. But a robot... is never going to have that problem.
I mean I get your point- a large enough conflict in Cybertronian history could result in the physically destruction of records and maybe even kill off large segments of the populace alive from an earlier age
but we're dealing with a technologically advanced robotic race here.
We're just bald monkeys limited by our biology but we're starting to make breakthroughs that push data storage beyond the physical. Cloud technology is just the most latest step in potentially all of our information- or at least backups of it- being stored in spaces beyond the physical. So if we're pushing that frontier I have to think a robotic species that's cracked FTL travel has a firm handle on data storage that won't just be gone forever after a particularly brutal bombing campaign.
Finally... creative freedom.
You tell a story about the Autobot/Decepticon War on Earth and you need to keep it recognizable as present day Earth.
But if you tease out the idea that this war would have to be half a billion to a billion years old to pass into the realm of myth and legend to the Maximals and Predacons you can do SO MUCH that isn't constrained.
Half a billion years- let alone a billion years- is so far into the future that you can tell any story you want. What's humanity like? Is it even recognizable as humanity? What's Cybertron like?
You'd have a totally clean slate to tell pretty much any story you'd want.