Why was it explained that Vin was special to Preservation in 'The Hero of Ages'?

Vin was special to Preservation because she possessed both Allomantic and Feruchemical abilities, making her a unique and powerful Mistborn. Additionally, Preservation saw potential in Vin to make sacrifices for the greater good, allowing her to become the Hero of Ages who could defeat Ruin and save the world. This connection with Preservation gave Vin the strength and determination to carry out her pivotal role in the story.