I'm sorry, but this is just so wrong. I'm not saying humans can't eat meat, but if you compare the digestive track and other physiological factors of humans to animals that actually evolved to eat meat like lions the difference is startling. On the spectrum of cow to lion we are very far from the lion end so to say humans "evolved to preferentially run on fatty meat from large game animals" is just plain wrong.

Here is a somewhat entertaining video with some specifics and sources. https://www.youtube.com/watch?v=XmXynDLkbXY

There is also a ton of anthropological data on how our diets actually did evolve and although there are exceptions the gist is that we mainly relied on gathered plants with occasional meat.

I've spent a lot of time reading about keto etc

An important detail in many of these studies (I'm not sure if it applies here, it's not clear on the paper) is that mice High Fat Diet isn't high fat as in keto.

Keto is: high fat, almost zero carbs, many vegetables (normal to low calories and low insulin peaks)

HFD in mice studies is: we put more fat in the normal mice food to give them more calories so they get fat (very high calories with insulin cycles)