The way I understand this is that China realizes the election in the US will not go their way and so they must act before the people elected in November get into power. I would even say that he may feel he must act before Nov 8 because after that even though they are not yet inaugurated everyone will view them as being in power. This will also mean that Trump, whether he is a shadow president or merely a leader of a populist movement is really far more in charge than Biden.
What was his action? He very publicly removed the prominent and respected members who are arguing against a nuclear war.
Xi has a couple of goals. Take over Taiwan and become the supreme power in the world. He must act now. China's economy, real estate market and banking system is all on the precipice of collapsing. Therefore if they do not act now it could easily be 20-50 years before they get another chance. They are also on the verge of a famine. People do not appreciate the severity of the drought in the Yangtze river basin and how big the impact of this is on China. If Xi does not go to war with the US and seize Taiwan he will be blamed for all the ills: famine, economic collapse, and once the MAGA candidates are firmly in power they will also have hearings on Covid19 and very likely bring massive crippling lawsuits against China.