Martin Luther - He complained that the pope was the main mediatopr of God’s will rather than the book of scriptures, and that he nailed to the entryway of the Wittenberg church; the act that begun the Reformation.
John Calvin - Calvin complains that rather than instructing and pursuing holiness, the authority within the Roman church exercises “a most brutal tyranny” over the souls of the individuals of God, claiming powers and authority not given to them by God.
Please correct any mistakes in my answer!! I'd be happy to fix it!! :)
External factors:
The 1905 Revolution - Russia's first steps towards a constitutional monarchy was more or less snuffed out after the Tsar dissolved the First State Duma. The following Dumas were politically neutered and had very little real power.
The February Revolution was swamped by the October Revolution because it lacked democratic legitimacy. The Provisional Government was the re-constituted last State Duma. It refused an election to a promised interim government - the Constituent Assembly - saying that Russia would hold elections after the war.
The Petrograd Soviet was seen by many as a genuinely democratic institution, as it's members were elected to it from the garrisons and factories of the capital.
The Bolshevik slogan "Bread, Land and Peace" sum up the other external factors: The cities were starving as the peasants were now in uniform fighting in the war - they could not plough, sow or harvest the crops. And the food delivery infrastructure had broken down. The peasants wanted the Provisional Government to give them the land they worked on - it didn't, and the most of the land was still owned by the aristocracy. And Russia was doing badly in the war and most people wanted Russia to withdraw from it.
Internal factors:
Lenin was a dedicated, determined and capable leader. He motivated his party and, through agitation & propaganda, the Bolsheviks became very popular in the army and in the factories.
Trotsky was an extremely gifted administrator. He was the chairman of the Milrevkom - the Military Revolutionary Committee - this was the organisation that orchestrated the events of October 1917.
The leadership of the party was loyal to Lenin, and they followed his orders with conviction.
The party had a competent propaganda machine, producing newspapers, banners, posters and setting up recruitment drives in the army and factories.
