Catalog pins show up when people are searching for “shopping terms”. Lets say you search for “:red dress”. you will have two tabs that open up – one will be explore and the other will be shop. Under the shop section you have product pins tha have been added by shop owners. Your pin can show up in any of these searches based on how relevant your product is to the user. So thats what is driving your traffic. If engagement goes up for one product, all related products start getting more views as well.