are very energy dense food sources.
Doesn't mean that it's a good idea. When you feed food to food, you waste a lot of food. That's the meat, dairy and eggs industry. Conversion ratios vary, but they're terrible and, by the simple laws of physics, can't beat just eating plants.
universal purpose vegetable based butter
That is what did happen, but it turns out that hydrogenation causing trans fats isn't good for health. Fun fact: ruminant milk, especially from "grass fed", can contain up to 10% trans fats because the bacteria inside can do a natural hydrogenation too.
Vegetable oil is the best option for calories, but it's also boring, so the staples for food security have been: grain flour + vegetable oil + sugar.
Here's some relevant history: https://encyclopedia.1914-1918-online.net/article/naval-blockade-of-germany/
and a more modern article tied to the same topic: https://www.bostonreview.net/articles/troy-vettese-do-not-let-them-eat-meat/
I don't disagree, I'm just pointing out that hydrogenated fat ("margarine") is a problem.
https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-021-01961-2/figures/1