I don't think American politicians are that much different, during the election campaign many candidates will try to win votes so they make promises to win the hearts of the citizens. It does not guarantee they will stick to their ideology once they are in power. Western politicians can be bribed as well, they just call it lobby
Social unrest come and go, as long CCP can manage to lift more poor out of poverty despite rising inequality between the rich and the poor, the party can rest assured of maintaining in power. Therefor reforms are necessary, dealing with corrupt politicians who are abusing their power for selfish gains, more development in the rural area which is what are seeing in the western part of China. Since ancient times when the population was dissatisfied with the emperor (usually lack of food due to weather), he would be toppled down and a new ruler emerges. Because we have abandoned the Dynasty system it would be illogical to topple the whole Party system and replace it with another Party or switching to a Democratic style. As long Chinese economy can sustain its growth, the basic 4 layers of Maslow's piramid should be met for the majority of the population hence a coup is deem unlikely.