American Idol was based on the British show Pop Idol created by Simon Fuller, which was in turn inspired by the New Zealand television singing competition Popstars. Television producer Nigel Lythgoe saw it in Australia and helped bring it over to Britain. Fuller was inspired by the idea from Popstars of employing a panel of judges to select singers in audition. He then added other elements, such as telephone voting by the viewing public (which at the time was already in use in shows such as the Eurovision Song Contest), the drama of backstories and real-life soap opera unfolding in real time. The show debuted in 2001 in Britain with Lythgoe as showrunner‍—‌the executive producer and production leader‍—‌and Simon Cowell as one of the judges, and was a big success with the viewing public.
Is there an answer to this question (If it cannot be answered, say "unanswerable"): What show was Pop Idols based on?
Popstars