Here's why:
* Bottomless Trap Hole's Effect: Bottomless Trap Hole activates when a monster is Special Summoned. It then destroys that monster.
* Darkness Special Summon: Darkness monsters are not "Special Summoned" in the traditional sense. They are summoned directly from the hand or deck to the field using their own unique summoning conditions.
Examples of Darkness monsters and their summoning methods:
* Chaos Sorcerer: Special Summoned from the hand, requiring a specific condition (a specific number of monsters in the graveyard).
* Dark Magician: Special Summoned from the hand by tributing another Dark Magician.
Therefore, since Darkness monsters do not use the typical Special Summoning method, Bottomless Trap Hole will not activate against them.