In the original Lavos timeline, the early humans still witness the Fall of Lavos, and name him Lavos as a result. Ages later Lavos' power is tapped into in the kingdom of Zeal. Presumably the Fall of Zeal happens much as in the keystone timeline, with survivors living among the Earthbound. Knowledge of Lavos should be intact up until this point. The survivors of Zeal know for a fact it exists, and the Earthbound should too, even if they've never directly felt its power. All of them should be aware that Lavos is still there, deep inside the planet's core.
Yet somewhere, over the course of 13,000 years, this knowledge was lost. It seems like it wasn't even reduced to a legend, because nobody in 600 AD or 1000 AD even refers to it as such. If humanity had known about Lavos' existence, I feel like somewhere down the line they could have staged an admirably pre-emptive attack, or even a defense in anticipation of its impact. Yet by 1999, the world was caught completely off guard.
How was this knowledge lost throughout the ages? Did the surviving Zealians and Earthbound not think to warn future generations of the danger sleeping deep inside the planet?
It's especially strange considering Melchior was displaced to 1000 AD, so they had a Zealian alive and well in the present day era who had been fully capable of warning the world about the threat Lavos posed. Yet he seemingly sat idly by as the world lived in ignorance until the Day of Destruction.