Some Russians did not like the previous Tsarist government. In the 1900s Russia was poor. It lost the Russo-Japanese War. They only recently ended serfdom, where peasants were forced to farm for nobles who owned the land. Since Russia is pretty far north, growing food was not easy, and they were often hit by famine and food shortages. The government was also corrupt: the tsar Nicholas did not listen to the parliament, and Rasputin was murdered. They industrialized later than western Europe and the US. So when Russia entered World War I, they lost a lot of soldiers fighting Germany, which was more industrialized. For all of these reasons, people got angry and blamed the tsar.