@taoeffect the bigger instances have the advantage here because it's already a thing on the "trending" page, but it's only calculated by likes originating from your instance.
Though, I think it's that way because likes are only federated between the instance that the post originates from and the instance that the "like" comes from. So when you see a post with a number of likes, you know that they came from your instance or the post is from your instance.