Explanation: In addition to being a remarkably efficient foodstuff, the potato's introduction to Europe was also a boon on a non-nutritional level - namely, that it avoided many of the traditional problems with grains. Rampaging army going through your lands? They can't burn your field, and they don't have time to dig up all your potatoes! Shitty soil? Potatoes are brutally hardy plants, they'll make it through. Called off for corvee by your government before the harvest? No worries, the potatoes will remain until the frost!
The Prussian (German) king Frederick the Great, despite being associated with military glory in the modern day, was intensely interested in, and involved with, 'rational' reform of civilian society, including more productive forms of agriculture. He put great effort into spreading the cultivation of the potato throughout Prussia - an effort which paid great dividends in improving Prussian agriculture.
Amusingly enough, his success there intersected with his success in warfare - a French military doctor, one Monsieur Parmentier, was captured during one of Frederick's wars with France, and fed a steady diet of potatoes in captivity. As the potato was considered by many to be unfit for human consumption at this time, Dr. Parmentier was astounded to find, once the war and his captivity had ended, that a steady diet of potatoes had actually been quite healthy for him and his fellow PoWs! Armed with this discovery, Dr. Parmentier spread the use of potato back in his native France, and advocated for its use across all of Europe!
Thanks, doc!