Why Did Stalin Become Leader after Lenin, not Trotsky?

In the beginning, as Lenin end grew nearer, there were five potential leaders, Bukharin, Kamenev, Zinoviev, Trotsky and Stalin. It seemed so obvious that there only was one man to take over Lenin's reign - Trotsky. He was Lenin's right hand man, but a close second was Stalin. People saw him as the one who came second, that's all he was; there was no way that he would beat Trotsky in the race for leadership, but what they didn't know that Stalin's cunning would overtake then all and he would end up being the leader of Russia.
Stalin knew he would have to worry about the other three, as separate candidates. Trotsky was his main rival. …