It’s not strange at all - it’s a meat/nut/greens diet similar to what our ancestors ate before developing wheat and starch crops.
Thanks to our advancements in agriculture we’ve made our wheat, corn and rice super energized and easily digested - these get broken down immediately into sugar in our system and, if not quickly burned off, get stored as fat by the body. It’s very easy in this society to overeat these items (remember the old food pyramid) which is why we’re all growing so fat. (Lack of movement is helping there too)
Keto, as Atkins proposed it, was only meant to be a temporary diet until the fat could be burned off and then those items could be reintroduced sparingly.
There’s also speculation that there’s something in the refined grains that’s harmful to the systems of some people which is why they some benefits when switching to an all meat diet. (Whether a genetic issue, or how the grains have been hybridized or possibly something with the pesticides used on the crops)
Monsanto.