Even though Stalin did not contribute to the Bolsheviks / Communists, seizing power in 1917 or by helping them win the Civil War, he was still able to be seen as an important part of the party whom many respected. Before Lenin’s first stroke in May 1922 nobody more than Lenin himself admired the attitude that Stalin had. This attitude made him very popular with the party members because Stalin was far too useful, hardworking member thus the reason he was one of six men to be on every delegates list. However shortly after Lenin’s first stroke when he became incapacitated was when he realised Stalin’s true colours and he began to turn against Stalin. Lenin knew that when he was healthy he could control Stalin because he was a powerful cult figure but with him being out of action he was unable to control him. This was when luck became a major part of Stalin gaining power.
On January 21, 1924, Lenin died. The first major piece of luck for Stalin came was the timing of his death, due to the fact Trotsky was away that month, and Stalin telegraphed him and said that the funeral would be held immediately, so there was no point in undertaking the long trip back to Moscow. Thus Stalin forced Trotsky to be absent for the funeral. Another factor that could of ended Stalin’s rise to power but he had effectively started was Lenin’s Testament. Lenin's Testament, with its warning against Stalin and suggestion that he be removed from leadership, was read at the next Central Committee meeting. This was a critical moment, if his rivals had demanded compliance with the testament at this point, Stalin would not have survived their attacks, even though he had a power base it was not yet large enough to withstand these attacks. However with luck on his side, Trotsky kept silent because the testament would also cause problems for him too, and Stalin's allies, Kamenev and Zinoviev, came to his defence.
The following year, 1924, marks the beginning of Stalin's rise to power. At that point he was one of seven members of the Politburo. The others were Zinoviev and Kamenev, Trotsky, Nikolai Bukharin, Alexei Rykov, and Mikhail Tomsky.
Stalin’s amazing success can be attributed to a combination of his own political genius and the mistakes that his rivals persisted in making. Luck may have been a massive part in Stalin acquisition of power but you cannot forget his political aptitude.
In December 1924, Stalin first articulated his own twist on Marxist orthodoxy, which he termed "Socialism in One Country." He argued that the success of Marxism in Russia was not contingent upon a worldwide Communist Revolution-- which his fellow leaders expected to begin sweeping through the rest of the world at any moment. The global fall of capitalism would come eventually, he said, but in the meantime it was necessary to build a successful Soviet Union. Trotsky and his supporters vigorously attacked this viewpoint, but by this time, Trotsky's star was in eclipse. Always considered an outsider by the older Bolsheviks, he had been a brilliant military organizer, but was proving less adept at the cutthroat world of party politics. By January 1925, Zinoviev and Kamenev were urging that he be expelled from the Politburo. By this point, Stalin was gravitating away from the "troika" and toward the other three members of the Politburo--Bukharin, Rykov and Tomsky. These three formed a so-called "Rightist" bloc, differing on economic policy from Zinoviev and. The "Rightists" wanted to continue with Lenin's New Economic Policy, which allowed considerable economic freedom for the peasantry, while the Zinoviev and Kamenev the "Leftists" wanted to push the country more strongly toward state control of economic life.
In 1924, the "Leftists" appeared to hold control over the Central Committee. But by the following year, Zinoviev and Kamenev realized that Stalin, whom they had saved from political ruin after Lenin's death, was betraying them and moving toward an alliance with Bukharin's faction. In addition, Stalin had begun to gather a strong faction around himself, including figures like Mikhail Kalinin, Kliment Vorishilov, and Vyacheslav Molotov. While Trotsky, the weakest member of the Politburo, remained aloof, the Rightists and Leftists clashed at the 1925 Party Congress, and the Rightists carried the day, despite vituperative attacks on Stalin and his "Socialism in One Country" by Kamenev. Kalinin and Vorishilov joined the Politburo, and the suddenly weakened Kamenev and Zinoviev turned to Trotsky for support, forming a "United Opposition" in the summer of 1926. But they were no match for the Bukharin-Stalin alliance. By the time of the next Party Congress, in October of 1926, Zinoviev and Kamenev had been removed from the Politburo, and Stalin felt secure enough in his power to urge the Party's official repudiation of their views as "anti-Leninist." Trotsky resisted, and in 1927 he was expelled from the party and exiled to Central Asia; Zinoviev and Kamenev, defeated, begged for clemency, which the Politburo granted. Stalin was triumphant--now, even his ally in this struggle, Bukharin, grew nervous, as he realized that Stalin's power in the Party now overshadowed even his own influence.
Overall there were many factors that helped Stalin’s acquisition of power but I do not believe that the base of power he had before Lenin’s death was the most important reason. Without luck or having the right political I am certain Stalin wouldn’t have been able to build up so much power in such a short period of time, let alone survived Lenin’s Testament.