I work for an online retailer that sells thousands of products from hundreds of brands. We've been advertising with AdWords (Google Ads) and Shopping for the better part of a decade with great results.
Over the past few years, some of the best real estate has shifted to the featured listings in the product knowledge panel:
The red box in the above screenshot is free real estate for stores that have their Merchant Center Feed and structured data set up correctly. If you click "Compare prices" at the bottom you can see dozens or hundreds more sellers/listings, so this featured box of 5 listings is stiff competition.
So my question is: What are the factors that lead to a listing being featured in that box?
I assume that price and shipping policy play a role. But I can't figure out why I'm having such a hard time getting featured. Even when we have the best price and free shipping, our success rate of landing in that box is pathetically low. I can verify that we're handling the Merchant Center feed correctly, since we show up in "Compare Prices" and we are occasionally featured in the box.