The reasons for the revolutions are many, but we can point out some as the form of government; Russia was one of the last major European countries where the monarchy was an autocrat, his power not limited by laws or institutions. Another fact was the total inefficient emperor and Tsar of all Russians, Nicholas II.
Also, the development of an "educated middle class", result of the industrial revolution in Russia, provided the social basis for the creation of a liberal political movement demanding political rights and constitutionalism.
Finally, the world war I was the central reason for the revolution and its outcome. Russia was completely unprepared military, industrially and politically. By the end, the empire had lost large and rich portions of land and millions of men. This chaotic scenario made the revolution inevitable. The generalized dissatisfaction forced Tsar Nicholas II to abdicate and created a vacuum of power that led the Soviet party to slowly take control of the Russian administration.
