Fitness has fashions and trends. It's not exactly a secret. Everyone wants to have something flashy, new, and exciting to offer, even if the basics of exercise are fundamentally unchanged for thousands of years.
The trend generally operates like this:
1) Great new thing! Someone "discovers" a great new thing, which is generally an old thing that just fell out of fashion at some point. Or never fell out of fashion at all, but is renamed as something new.
2) Proliferation. Soon, the great new thing is everywhere.
3) Questioning. Is this great new thing really that great?
4) Backlash. This Great New Thing isn't new, or great, and is in fact bad for you!
5) Fade out. The Great New Thing starts to be become unfashionable, and people pushing it are regarded as dinosaurs, grumpy old trainers, and hopelessly out of date.
6) Re-examination. Once again, people begin to look at the now-unfashionable training method and realize, hey, there is some real value here. After this, proceed back to #1.
You can see this all over the play. Jogging is the way to get in shape. Everyone, let's start jogging! Here are books and videos on jogging. Hey, is jogging all of that? Jogging, does anyone still do that? Hmm, hey, look, there is some value in jogging. (Fill in bodybuilding-style training, circuit training, hot yoga, cool yoga, functional training, athletic training, etc. for "jogging.")
This isn't to say there isn't value in re-examining and stressing old things, or questioning the value of exercises and apporaches to exercise. There is a lot of value to be found in that. And sometimes, hearing an old thing in a new way is what triggers understanding in people who didn't have that understanding in the first place. Or it allows an audience that didn't have access to that information to get it and understand it.
And generally there is some core of people who keep doing it - no matter how much people pushed, say, long and slow cardio out as a muscle-killing time-wasting joint-wrecking exercise, you'd see boxers doing roadwork because it had worked for fighting sports for millennia as a way to last in long fights. There are always people doing bodybuilding, whether it is in the "in" thing or not. And so on.
And certainly, not everything works - some training methods, old and new, a based on spurious reasoning and/or poorly done research.
Be wary of claims of something thing entirely new, the best thing ever, or how the new thing is bad and needs to be ignored. Remember that the fundamentals underlying the success or failure of training methods don't change. Only the names attached to them and how fashionable or "in" they are changes. Look at any new trend and just know, it's just fashion, not a shift in the reality of adaptations to training.
It's probably just a trend - and whatever makes it work (or not work) will remain regardless of how fashionable it is. Find what works for you, for your goals, and use that . . . not what is the most popular method on hand.