Just click your heels and a new study appears with the opposite findings.
https://med.stanford.edu/news/all-news/2018/02/low-fat-or-low-carb-its-a-draw-study-finds.html
https://newatlas.com/low-carb-ketogenic-diet-lifespan-memory-study/51215/
For every expert there is an equal and opposite expert.
Yes, because when it comes to diet, there are almost NO actual clinical studies. Clinical studies control all the variables, have control groups, take years and years of constant monitoring. The studies that said fat caused heart attacks weren't clinical and they were taken as gospel on the premise that if we didn't change everything due to them and they turned out to be right, the consequences of that mistake would be too great. That's fact, it's what the guys who wrote the studies said. Yet we turned the entire American diet upside down to be focused mostly on grains based on unreliable epideiological studies. And as you point out, there are different studies that all say different things because they aren't really scientific.
My personal experience says that low carb / high fat resulted (for me) in 80 pound weight loss, pre-diabetes gone, A1C and blood sugar totally normal, perfect blood work by every metric used, borderline hyper-tension cured. But I'm supposed to believe a study that says they think somehow all that is likely to shorten my life?