After the fall of the German Emperor in the Great War, the revolution in Germany led to a greatly progressive document for its new constitution in the city of Weimar. It called for sweeping checks and proportional representative government, ideas evolved during the strong years of Germany before the war.
Just before final approval, the National Assembly voted to take a final review in committee of this problem of extremism. After much discussion, they decided to postpone truly proportional representative government until the finances of the country were balanced and the war reparations paid. Until then, Germany would have tiered elections aimed toward moderate, unified leadership. To hold back single-handed power from another kaiser, Article 48 (giving the president power to "take all necessary steps" in the case that "public order and security are seriously disturbed or endangered") was more carefully defined and limited to true moments of panic or war.
The new constitution was ratified and came into affect in August of 1919. When elections came around, it was seen that the radicals on both the left and the right were taking wild stands. Fortunately, the follow-up elections allowed for control over different angles and solid centrists to take command. Many former low-level leaders before the war were returned to office, and they set about to restore the strength of Germany despite the odds.
Initial problems broke out as violence challenged the strength of the new republic. The communist Red Guards and the right-wing Freikorps both instigated attacks on each other as well as civilians. Rather than simply arresting whomever they could to try to bottle up a torrent, the German government set about on a program of “Rationalization” where disagreeing parties were drawn together to discuss their differences. While that served as the cover, many times the plan was used to pit the extremists against each other, such as the Freikorps paramilitary being used to bring down an attempted communist coup in Bavaria. Whenever possible, the government would then arrest leaders and exile them, sending many to Soviet Russia or increasingly conservative Italy.
With balance vaguely achieved (though the process was continual... a young artist named Adolph Hitler was arrested in Bavaria a number of times and exiled to Austria in 1923, for example), the government focused on its economic policies. Hyperinflation was controlled by freezing prices and continually discussing reparation treaties with other countries, gradually talking down the amount rather than paying fully as international tempers cooled.
In the 1920s, elections would broaden as the Goldene Zwanziger was in swing. Few were interested in extremism while the country grew prosperous. As the markets crashed and the Great Depression set in, however, the political climate changed. Still, with even its short tradition of leadership, the dark age only strengthened the German peoples' faith in its government. A gradual system of social nets began to grow, mirroring the public works projects put up in the United States by their president FDR.
The world economy would gradually pick itself back into place in the 1940s, helped a good deal by the international demands for food, steel, and cloth in the Italian campaigns in Africa (to which many German right-wing expatriates would go, alleviating unemployment) and the Pacific War. Fought by the Japanese against the Americans, British, and French, the financial and material needs of their countries would give Germany a boost back into solvency. In fact, the war would even prove the shortcomings of the League of Nations, which would be strengthened by the Treaty of Kyoto in 1944.
When the Soviet Wars of the 1950s broke out, Germany found itself on the front lines after the conquest of Poland. The armies of Stalin and later Khrushchev, began marching west and south, conquering and even entering the Mediterranean. Joining with former enemies France, England, and the United States, Germans fought for their nationhood, holding out for long years against sieges and bombings by Soviet forces. With the defeat of Soviet Russia and the fall of communism in 1971, Germany and the Allies set to rebuilding the world.
In reality, the Weimar Constitution was academically brilliant, but did not have the practicality for the real world. Hyperinflation would cripple Germany, which would be fought over by extremists each thinking they had the best idea. Through propaganda and chutzpa, the once tiny National Socialist party would gain power under Hitler, strengthening Germany but forever changing the history of the world.