If it doesn't happen that often that a new dictator manages to topple a current one, it's because the current dictator (a) already had a good power base/large s

If it doesn't happen that often that a new dictator manages to topple a current one, it's because the current dictator (a) already had a good power base/large support among the elite before he came to power and (b) because, as soon as he is in power, he's careful to keep his supporters among the elite happy and eliminate any possible contenders. Even Kim Jong Un, who had a good position by being built up as "heir" during his father's "reign", had to eliminate a few (true or imagined) competitors (https://en.wikipedia.org/wiki/Kim_Jong_Un#Purges_and_executions https://en.wikipedia.org/wiki/Kim_Jong_Un#Purges_and_executi...).