The single biggest issue that Maou has to deal with in her quest to end this war is (arguably) tradition, this coupled with the idealism of those who continue to believe in the righteousness of this war make all of her plans worthless, at least for now. Before she can ever get around to solving basic problems such as crop rotation, food shortages and by extension the wealth and wellbeing of society, she must first educate everyone on the basic principles of war, economy and social responsibility. Yuusha claimed to be a righteous warrior, one bent on the destruction of Maou, thus freeing his country and continent from war and oppression. His claims are not merely his, but a product of commonly held beliefs and ideals surrounding the nature of the demon realm, and how it pertains to the prosperity of their own nation. Ideals are dangerous, especially when they are linked to warfare and the trade that goes on around it. The ideals of Yuusha are particularly dangerous and easily manipulated as we saw in the last episode when Maou pointed out that he was the only one dispatched to kill her, when the best course of action, assuming those in power wanted to end the war would be to send a well equipped and powerful army.