Many historians argue that the actions of Tsar Nicholas II weakened the Russian government and helped to bring about the Bolshevik Revolution of 1917. In this answer, I will discuss two related actions by Nicholas that happened just before the Revolution and which helped to bring it about.
The first action on the part of Nicholas was his decision to take control of the Russian army in 1915. The Tsar felt that the army had been doing badly and that it would be better if he took personal command. He felt that this would motivate the army to fight better and be more successful. Unfortunately, Nicholas knew very little about military affairs. This helped bring about a series of humiliating defeats. Because Nicholas was directly in control of the army during this time, he was blamed for those defeats. This weakened the Russian government because it reduced people’s trust in Tsar Nicholas. It made them think that he could not really do a good job of running the country.
The second action that Nicholas took was to leave the capital (St. Petersburg) to head the army, leaving the Tsarina in charge of the government. This was a mistake because Tsarina Alexandra wanted very much to maintain royal autocratic power. Because of this, she made sure that the high governmental officials under her were weak men who only held power because she liked them. This weakened the Russian government because it ensured that the government would be led by men who lacked the ability to be good leaders.
In these ways, Nicholas II badly harmed the effectiveness of the Russian government by taking control of the army and by leaving his wife in charge of the civilian government while he did so.