Heroes ran for four seasons on NBC, before being canceled and was followed up by a revival, only to have it canceled again. Heroes was wholly unique for its time. A few years before superhero movies took over the film industry, the series was part of a much smaller superhero boom in the mid-2000s. Following in the footsteps of shows like Smallville, Heroes proved that superhero stories didn't require the budget of a theatrical movie to work.

https://screenrant.com/why-heroes-cancel-season-4-reborn/