Template:Follow the Leader
Whenever a work achieves enough success, there will be imitators. It doesn't matter if it's a cheap foreign knockoff or a major Hollywood production. It doesn't matter whether the writers are choosing to do this or the producers are. If they think they can make money ripping off a successful work, or at least something else in its genre, they will do so. Thanks to Sturgeon's Law, this has the typical effect of flooding the market with a lot of inferior works. But not always.
Of course, the trailblazing work may itself not be original; in this day and age, little is. But it just manages to capture the public's interest (and their money), and it is this magical moment that studios strive to duplicate, after the fact.