Earlier quoted context omitted.
Japan did massive fiscal stimulus ("bottom up") and capital injections ("top down") from the BoJ and it still has crawled compared to other economies. China has for years done intense injections into its economy (both top and bottom down), with worker training programs, state owned enterprises, etc; and now they became so reliant on the artificial demand created by their own government that they have huge slack in in…
"If the government bought wheat, for instance, to keep its price high and keep farmers employed; then burns it, this creates asset misallocations, though it is technically creating demand (this still happens to this day.)" This has been done successfully but without the burning. Just keep the price stables buying when the price fall and selling when the price goes up. The idea of a buffer should be easy to understand…
And there is no need for the government to be involved in that either. If there was really predictable price fluctuations between years, investors could make money buying up commodities on good years and selling during bad years (and they do.)