Fierro succeeded Chris Brancato, who left in April for an overall deal at ABC Studios. Brancato had joined the Pablo Escobar drama midway through production on Season 1 and is credited as co-creator alongside Carlo Bernard and Doug Miro who had written the original script. The showrunner change was made before Narcos had debuted. I hear at the time Netflix and producer Gaumont International Television were looking to change things up for Season 2, and The Shield and The Walking Dead alum Fierro was tasked with charting the new creative direction.
After Narcos premiered to large viewership and good reviews, there was a push for stronger continuation in Season 2. Jose Padilha, who was to step back after serving as director/executive producer in Season 2, was brought back.
According to Netflix, Fierro has completed the services on Season 2 that he had been contracted for. (That is understood to include breaking stories for the new episodes as well as writing services.) Padilha and fellow returning executive producer Eric Newman are now taking over, working with the show’s writing team. The series is half-way through Season 2, on which Bernard and Miro serve as consulting producers/writers.
Narcos recently landed two Golden Globes nominations, for best drama series and best actor, Wagner Moura.