Apparently (per the Wiki) the fad grew after 2020, when Joe Rogan (an American podcaster) interviewed Paul Saladino (an American "carnivore diet" promoter and current food supplement business owner).

The Wiki claims that this fad diet / conspiracy theory is popular on the "political right". Actually, my guess is that a better description would be that this is particularly popular among certain social media "wellness influencers" and "alternative health" promoters. Especially wellness influencers who have been pushing anti-veganism / meat-only / high-protein fad diets in the past.

There seems to be overlap between this movement and anti-vaccination movement promoters (Joseph Mercola, a key figure in the later movement, is now also promoting anti-seed oil activism).

I don't see a whole lot of influencers promoting this yet who are not American. I also don't see this fad outside social media much personally, despite being an American. The primary thing I can think of is that the fast food chain Steak N Shake is heavily touting its "beef tallow fries" on their billboards now.