In an explanatory essay, or any essay, the introductory paragraph introduces (hence it's name) the main idea, or what you are going to explain. The body paragraphs go into extreme detail of what the introductory paragraphs mentioned.
The reasons that totalitarian states arose after WWI are many. The economy of many countries was shattered by the costly conflict (especially Germany, being forced to pay reparations), causing socialist and communist ideas to flourish. The scars on society left by the war allowed for embittered populations to be swayed by good orators that could play to the crowd's emotions; Hitler liked to appeal to a desire for revenge in the German people, for instance. Also, as mentioned before, new ideas spread during the war, many involving government, often causing factions to fight over a country, with one finally coming on top, usually led by a single, charismatic individual.
Answer:
Historical interpretation
Going through the great depression
That a dynasty can translate into lots of income for another thousand years by naming restaurants after said dynasty. Hope i helped