You know all this because...? You realize that the end point of radical skepticism is that you can't rely on anything at all, not even the directions on your appliances. Nor even your own memoranda (they could have changed them behind your back). You have no point of contact with reality. You have a mental problem.

But to come back to the thread and not let it go into a memory hole... You said "There's absolutely no record of [Eratosthenes] existing until they made him up in the eighties or whatever." This is manifestly false when references him go back to the 1st century. So, you were not merely mistaken, you simply lied outright, making a statement entirely without foundation. Your "assumption" was a fantasy, having no relationship to reality. So, to say "it's not even a stretch to assume" is frivolous nonsense.

But that is how you work. When something is inconveniently an obstacle to your fantasy, you pretend they don't exist---and expect the rest of us to join in your pretense. This is called solipsism, the doctrine that the world is what you think it is. It is a mental problem. You are not enlightened. You are just crazy.