Apparently 80,400 obsidian-knife sacrifices in 4 days is more believable than industrial genocide.
Nzi Germany was one of the most heavily industrialized nations in the world, ranking just behind the United States in steel production, engineering, and chemical manufacturing. They had railways, Zyklon B, crematoria designed by engineers, and a bureaucratic machine that tracked every deportation down to the individual.
Yet Holocaust deniers say 6 million was logistically impossible. Meanwhile, they think the Aztecs sacrificed 80,400 prisoners in four days with just obsidian knives and human muscle.