There's a much deeper issue at work. I've been studying this topic for a number of years now. Long before I heard anyone say "keto". The fact is that we've been told we understood what healthy nutrition means long before there was any evidence to say so, and our dietary guidelines and our ideas about what was healthy eating have been founded on some very bad science all along.
The reason you keep hearing competing claims about what is good or bad to eat is because most of the studies have been observational studies, which is mostly only good for creating hypothesis and doesn't prove any cause and effect. Also, most of the articles people read are journalist's opinions about studies, not the actual studies. Media articles about science are generally poor, but in nutrition they are crap and jump to unscientific conclusions, even if the study didn't.
Bottom line. The field of nutrition science was hijacked decades ago by people convinced that eating fat and cholesterol, particularly saturated fat, caused heart disease. They were convinced of that even though no science existed that proved it or even made a compelling case for it. Those beliefs were institutionalized and made official nutritional guidelines for healthy eating. We've all taken it in so much it just seems obvious. People have lowered their fat intake, and necessarily upped the carb intake, and gotten sicker and sicker.
But they were wrong, and it's been apparent for a long time that they've been wrong. From the very first, when actual good studies were done to prove that eating fat caused heart disease, those studies failed to do so. To this day that connection has never been proven.
But the science has shown that people did better on higher fat/lower carb diets, and since this has become less taboo in recent years more and more science is being done on it now, and it's confirming the same thing. A proper human diet is not one high in carbs and low in fat. It's the other way around. In other words, "keto".
Keto diets are taking off now because more and more people are sick. Obesity and diabetes rates are at levels unthinkable just a couple decades ago. And many of those people have discovered that ignoring official advice and even their doctors, and following a keto diet, can make them healthy. That's not a fad. They've discovered what their bodies actually need to work properly, and the science backs this up. It always did. It's just that the science did not inform the nutrition advice we've always been given.
And sadly, the “Standard American Diet” has become the “Standard World Diet”, Europeans are starting to get fat, too.