I'm guessing the media has grossly misrepresented whatever original diet started the fad. I'm currently on a doctor prescribed diet that, among other things, features a lot of fat. The thing is, it's not just any fat, but the... oh, screw it. I'm not going to waste my time trying to explain the difference between an Omega-3 and an Omega-6 and why grass fed beef/dairy, coconut oil, avacados, etc. are legitimately different than cottonseed oil, soybean oil, grain-fed beef, etc.. I've lost nearly 40lbs now because I'm getting the nutrition I need and I'm not stuffing my face with extra calories just because I feel hungry for nutrients I'm either not eating or not digesting. Now I am a special case because I've got health problems, besides my weight, that are being fixed and contributing to the weight loss, but it really is true that fat makes you feel full. It's honesty hard to overeat without a lot of carbs, even if I can eat as much fat as I please (mmm, big hunks of lamb fat in my soup.)
TL;DR Fat is not evil, and there's nothing inherently illogical about a high-fat diet actually causing weight loss.