It was a vicious circle. When Lenin died, it was widely expected that Trotsky was going to become the next leader, however he was far from universally supported. When Stalin became leader, he had to remove the Trotskyites from the party and put his trust within his cleansed inner circle. Yezhov and later Beria had to justify their position and did so by convincing Stalin that there were forces within the Soviet Union that were a danger to him. Whilst there were no doubt people in the Soviet Union who wanted to remove Stalin from power, or even kill him, the extent was exaggerated by the leaders of the NKVD in order to demonstrate their value.