The tsarist regime was able to the 1905 revolution for a number of key reasons such as the support of the armed forces and key point that the opposition's aims were not to overthrow the tsarist regime itself. However in the 1917 revolution these points and many other factors are reversed against Tsar Nicholas II and he is unable to bring the rising masses of Russia under control and therefore the 1917 February revolution succeeded in forced the abdication of the Tsar and with him the Tsarist regime.
The first key factor in why the Tsar survived the 1905 revolution was the support of the armed forces. Even though the Tsar had just being embarrassed in the Russo-Japanese war his armed forces were still loyal to him. They showed this by the events of Bloody Sunday when troops loyal to the Tsar shot at the marching revolutionaries and even though it wasn't actually his orders this event still showed the loyalty the army had towards him and the Tsarist regime. Overall the armed forces lead a key role in the defeat of the revolution. However in 1917 the armed forces turned against the Tsar and refused to carry out his or their superior officers' orders that were loyal to the tsarist regime. The reasons for this were the fact that the Russian army for 3 years had suffered horrible defeats at the hands of the Germans during WW1. This lead to a lack of morale among the army and eventually the Russian army on the front was in a state of mutiny. Many soldiers deserted or simply refused to follow orders. In Petrograd similar coups occurred and the solders refused to shoot at protesters and eventually joined them. The Tsar soon realized that without the armed forces he could not bring the Russian people under control as he had done in 1905 and abdicated. Therefore it is easily seen that a major factor in why the Tsarist regime survived 1905 and not 1917 was the support of the military forces.