While genres can be known for a variety of works, they don't always start out that way. Usually they start out as loads of obvious Follow the Leader copies of a Genre Busting or making work, or a Genre Popularizer for a genre so small that this is the first time the mainstream has heard of it. Eventually all the followers stop being that, and start having loads of works that stand on their own. This is the point that you don't just have a bunch of clones, you have a full genre. The opposite is Genre Killer.