Pharrell has been around for 20 years or so, solo since 2003
This doesn't not make Pharrell a fad. PSY has been around since 1999. It doesn't mean he wasn't a fad with "Gangnam Style." Pharrell was a fad with "Get Lucky" and "Happy." This is all common sense, people, not some outrageous statement.
Pharrell had "Frontin" and a bunch of hits as a featured artist and as a producer. Pharrell has been well-known and a big name in the industry for years. If he's a "fad," then Ke$ha never ever ever ever happened. She really never happened, though.
Azealia never happened, hence the 11k and #30 peak position on the charts.