Warning: Contains spoilers for Wheel of Time season 1.
In The Wheel of Time season 1 finale, Lew Therin Telamon and 99 male Aes Sedai are revealed to have fought the Dark One, but the show does not explain what happened to them all. One of the animated shorts from The Wheel of Time Origins explains the history of Lews Therin himself and how his madness led to the breaking of the world. However, the story of those that were with him is not discussed.
The Wheel of Time season 1 finale gives viewers the first glimpses of the Age of Legends, a time when male and female Aes Sedai worked together in harmony to make a better world. However, Lews Therin insists upon taking a force of male Aes Sedai against the Dark One in the hopes of trapping him forever. The female Aes Sedai refuse to join them, insisting that the plan is doomed and someone will need to be around to clean up their mess. Latra Posae Decume, the head of the Aes Sedai during this time, is concerned that the Dark One might access the source of the One Power and corrupt it: a fear that was clearly well-grounded based on the tainting of saidin in the present day.
When Lews Therin and his Aes Sedai companions sealed the Dark One in a prison, in a final act of vengeance, the Dark One poisoned the male half of the True Source. As a result, Lews Therin and his 99 companion male Aes Sedai all went immediately mad as they had been drawing from the source and were directly exposed to the corruption at the time. The other male Aes Sedai also all lost their minds as they became exposed through channeling the corrupted power. While, for those further afield the process took a little longer, it was just as inevitable as for the ones that were at the Eye of the World. Over time, the female Aes Sedai found them and either gentled or killed them in an attempt to save the world.
Ishamael, one of the Forsaken, waits until Lews Therin in his madness has killed his whole family and then gives him a brief glimpse of sanity to allow him to realize what he has done. In his anguish, he unleashes the One Power. The momentous Dragonmount that overshadows the White Tower was the scene of Lews Therin’s death where he rent the ground into a new mountain, but male Aes Sedai everywhere performed similar acts and destroyed the world, ending the Age of Legends and beginning the Third Age, the period in which The Wheel of Time takes place.
The Wheel of Time TV series adaptation of Robert Jordan’s books has made some small changes that have little effect on how this played out. In the books, Lews Therin was not accompanied by exactly 99 male Aes Sedai. However, it makes a lot of sense within the construct of the narrative that over time the mythos surrounding the imprisonment of the Dark One and the Breaking of the World might have warped details such that Lews Therin and his accompanying male Aes Sedai are remembered as a nice round force of 100 users of the One Power. But regardless, Lews Therin Telamon and all of his companions immediately lost their minds to the taint of the Dark One on saidin with the rest of the male Aes Sedai slowly following suit.