The regime after the Cultural Revolution and the regime during the revolution were totally different people.
The majority of China's post-Cultural Revolution leaders had themselves been at least purged, but often also imprisoned and even tortured during that period. For example Deng Xiaoping had been purged and his son left permanently paralyzed (after a failed suicide attempt due to persecution) after the two became targets during the Cultural Revolution.
Basically anyone who had any sort of political power, educational attainment, or wealth was a target during the Cultural Revolution (a mildly difficult challenge is to find any Chinese figure of note who wasn't Mao who came of age before the Cultural Revolution and wasn't at least denounced. It's possible, but not as trivial as one might think).
The persecution was also often bottom-up, rather than top-down. If you had any attainment or pre-Cultural Revolution power at all, you were much more likely to be beaten, strung up, and imprisoned by local teenage Red Guards often acting of their own accord than the central government.
And so as a result there wasn't as much enmity towards the post-Cultural Revolution government by people who had suffered during the Cultural Revolution because often they had suffered together.