Why did Stalin win the struggle for power, 1924-1929?

In 1922 the leader of the Communist Party in the Soviet Union (CPSU), Vladimir Lenin, appointed Joseph Stalin as the General Secretary of the CPSU, which was a job that at the time no person with power wanted, so a not so well-known Georgian was given the position. In that same year, Lenin suffered a stroke and began a long physical and mental break down, in which the powerful Communist even started to have doubts about …

…struggle for power because he was given the position of General Secretary and utilised it to its full potential and was saved by Zinoviev in the Congress. Also because Stalin was helped by Zinoviev to make Trotsky resign from being the commissar of war in the army, and Stalin attacked Trotsky's theory of 'Permanent Revolution'. And finally because he took over Lenin's image and was shown to the Russian people as a new age Lenin.