OlfactionaryA concentration switch, not a different ingredient
Civet paste is dominated by indole and skatole, the same compounds responsible for fecal odor generally, alongside civetone, a macrocyclic musk. Above roughly 0.1% concentration, the sharp, animal, unmistakably fecal character dominates. Below about 0.01%, those components drop below the nose's detection threshold and civetone's warm, powdery, honeyed character takes over instead.
A very old trick
Civet's use in perfumery traces back to ancient Egypt, and is said to have been popularized by Arabic perfumers in the 10th century, who found it transformed into something genuinely desirable once heavily diluted and blended. It went on to become a staple animalic fixative in Western perfumery for centuries.