First of all, it's spelled Tsar. and now for the answer, there were many events that led to overthrow the Tsar, for example, the working class was very tired of non-equal pay and very bad working conditions. (Trust me, Russians have a very low standard.) This lead to the rise of opposing leaders, that are a bit nicer towards the working class such as the provisional government, and the communist party leader, Lenin.
They were to adopt the Fourteenth and Fifteenth amendments and select United States senators in preparation for readmission to the Union. On March 30, 1870, President Grant signed the act that readmitted Texas to the Union and ended Congressional Reconstruction.
The Axis Powers were spread over a large area. The Germans had not defeated Great Britain or the Soviets, forcing them to fight on two fronts. The Allies depended on U.S. production capacity and the size of the Soviets military.