4c Hollow One relies heavily on the graveyard for Vengevine and Detective's Phoenix, making Nihil Spellbomb a strong proactive answer that can strip their graveyard before those threats come back. Obsidian Charmaw provides a big flying beater that also destroys a nonbasic land, disrupting their manabase which runs many fetches and Sacred Foundry/Elegant Parlor. Thraben Charm's small damage mode won't reliably kill their bigger threats and Chthonian Nightmare is too slow against such an explosive graveyard deck, so both are cut. Prioritize graveyard disruption early since letting Vengevine chains go unchecked snowballs quickly against us.