This is true, but I don’t think the factors that led to the Khrushchev coup relied only on Stalin’s lack of persecution of political enemies. The very extremely centralized nature of the Soviet government, together with the excessive punishment of dissidents, led to the very dissidents hiding their true colors and conspiring against Stalin’s government. Had these people a voice to openly state their intentions, they could have been outmaneuvered, just like Stalin did to Trotsky’s coup. Understand that every action has a reaction and sometimes by trying too hard to prevent an outcome people end up causing it.