My question is: if the world was breaking, lines of communication across the globe were totally broken, chaos everywhere, Aes Sedai fragmented and messed up so bad that they gave the Aiel all their stuff THEN went off and forgot half of what they could do with the Power, how does history remember that Lews Therin went mad and killed his family AND THEN killed himself, creating Dragonmount in the process?
There was no one else around to see any of it except Ishamael, and there's no way that a lone man, Forsaken or not, let everyone on Earth know to the point that the story survived the Breaking. I mean, in tGH, Rand fights the "DO" in the sky for thousands to see, and still half the world denies it. So one man's word definitely can't be enough, especially the word of a Forsaken.
But fast forward three thousand years and even country bumpkin Rand, a guy who knows jack all about the world (didn't even know he lived on land that had once been a hallowed kingdom), is talking about Lews Therin Kinslayer going mad and killing his family before killing himself and making Dragonmount like security footage caught the whole thing.