it was just another fad that would not work and then would fade out.
It's been in use since the 70's. The diet is going nowhere. It works, but the gimmicky processed foods they tried to sell were a horrible idea. Most people only heard about it when low-carb became mainstream, but Atkins had been preaching it (and selling his diet books) for decades.
Low carb was around before Atkins...the diet was actually introduced in the 1880s by an Englishman named Banting. What happened to Atkins is what often happens when a charismatic founder dies...e g Ray Kroc...the company he runs goes into decline.