Contrary to popular belief, empires and great powers generally fall due to internal malaise and decay rather than from external pressures.
This was true of the Soviet Union, whose elites lost faith in their own ideology following their failure to mould Afghanistan in their image; this was true of Rome, which decayed over the course of centuries (and even Alaric, who sacked Rome in 410AD, had wanted to become a citizen); and it will be true of China as well. Great countries can survive massive external pressures. Short of war, only domestic discontent and self-doubt can cause their collapse. Viewed from this angle (and from a realist-functionalist interpretation), Xi Jinping's actions are completely in line with his self-interest if he believes that the threat to their existence is internal stability. And there is strong evidence that he believes exactly that: one of the first things he did upon taking the office of General Secretary was to make all cadres watch a six-part documentary on the fall of the Soviet Union. Hence nobody should be surprised at his decision to sacrifice China's international standing to shore up domestic stability --- and China has never been more domestically stable in the modern era, cf. a recent decade-long longitudinal survey from Harvard's Ash Center which looked at rising domestic satisfaction levels of local, provincial, and central governments.
This is before mentioning the broader trend of the so-called neo-authoritarian school of thought in Chinese policy circles as exemplified by the promotion of Wang Huning to the Politburo Standing Committee, taking a role equivalent to that of head of ideology; but the complex story of neo-authoritarian thought in China, along with Wang Huning's significance, is far too long to tap out on my phone. Suffice to say, all of Xi Jinping's actions are perfectly consistent with neo-authoritarian policy recommendations and only come across as a surprise to anyone who hasn't read up on it.
