I find this topic of fermented foods in different cultures pretty interesting. Surely they enabled people to survive a rough winter with food shortages. From an evolutionary perspective, it could be said that those peoples who didn't learn to produce fermented foods might've perished from starvation. It is an art that shouldn't be lost.
I really don't see the correlation with food shortages. Cabbage isn't nutritious at all. You'd need to eat 8 to 10 heads of cabbage to get 2000 Calories
As my sibling comment points out, it's full of micronutrients, which can be hard to come by when there isn't much growing. Having access to a decent source of electrolytes and vitamins really blunts the impact of having unreliable or inadequate food for a prolonged period.
It's not the cabbage per-se, it's what you cook it with. Like mushrooms, they have very few calories raw, but are cooked with some form of fat and that's what delivers the calories.
In Romania, pickled cabbage is a staple in the winter, cannot be that dissimilar to kimchi although I haven't tasted it. Particularly I like pickled cabbage juice straight from the barrel, some two months after they are prepared for fermentation. That's right around Christmas and it's the best thing to have after a hangover. There's also "drunkard's soup": cabbage juice soup, fatty and sour: https://www.bucataras.ro/uploads/modules/news/41634/656x440_...
Coming back to calories from cabbage, there's cabbage soup where cabbage is really, just for the flavor, like tea leaves in a tea you don't have to put a ton of them. That's one of the things I learned making my own soup, in the first one I put like a whole cabbage and turned out some yucky stew.
And there's sauteed cabbage, which I usually make in the fat left from frying sausages. And it's eaten with the very sausages, plus milk sour cream and bread. So a ton of calories, the cabbage is just ... I dunno, "the delivery agent" :)
But indeed it's not related to food shortages coze you don't have bread and cream and sausages when that happens. It's more like one of the several staples, coze although tasty, you can't eat potatoes all day, gotta vary.
Apparently protein as well? I remember reading that cabbage is the highest yield protein per acre. It's just wrapped in a whole bunch of greens you have to munch through first.
