Economic - During World War 1, the German economy was completely decimated. Massive hyperinflation there is so terrible that when employees receive three daily paychecks, their spouses merely spend the money on everything they can since prices are so high. And although its economy was in ruin, Germany had to provide reparations to the people it was fighting. And to top it all off, there is the great depression.
Political - Although it is far from the truth, the Treaty of Versailles forced Germany to take full responsibility for the war. The pact also required Germany to lose a sizable portion of its territory to neighboring nations including Poland, France, Belgium, and a few others. German speakers and people of German descent populated several of these countries. It becomes worse since one of Woodrow Wilson's 14 principles called for self-determination for all nations save Germany, including Austro-Hungary, a German ally.
Social - The aforementioned political motives caused many Germans to feel exploited for other people's political objectives. So it should come as no surprise that they chose a radical candidate when you repress a people like that.
So they can foresee something they might say or do and prepare to counteract a statement they might make or do something they planned to do first. A good (and funny) example is in an episode of Parks & Recreation where Leslie Knope announces that she's going to put a wheelchair ramp by every set of stairs in Pawnee but then the other political party campaign announces that they're going to put wheelchair elevators next to every set of stairs in the town.
The main purpose of both documents is to assert the rights and freedoms of the people to form their own governments -- governments which will protect their rights as citizens.
Historical context:
The Declaration of Independence (1776) asserted the American colonies' decision to break away from British government. It included the same Enlightenment ideals of natural rights and liberties that would characterize the Declaration of the Rights of Man and Citizen produced later (1789) in France.
The Declaration of the Rights of Man and the Citizen is a fundamental document of the French Revolution, which was written by Abbé Sieyès and the Marquis de Lafayette. Abbé Sieyès was a prominent clergyman in France who supported the rights of the common people. The Marquis de Lafayette was a member of the nobility who had fought in America's war for independence against Britain. Their document was written in consultation with Thomas Jefferson of the United States, who had drafted the Declaration of Independence.
Lincolns reconstruction plan was to offer the south and all former confederate's amenity or pardon. His plan also stated that southern states if having a 10% vote from it's citizens would be reimbursed into the union and a new constitution written for that state. Unlike the radical Republicans Reconstruction plan. Lincoln wanted them to rejoin the union as quickly as possible. johnsons plan took up the threads where lincoln took off. Johnson's plan was similar to lincolns but pleased congress and the radical republicans because President Johnson started sofisticating land from the wealthy aristrocratic Southerners. Hope that helped.