The TLDR is MAD equilibrium is being upset by US building out missile defense. US who has 20X more nukes than PRC is eroding PRC minimum deterrence doctrine via

The TLDR is MAD equilibrium is being upset by US building out missile defense. US who has 20X more nukes than PRC is eroding PRC minimum deterrence doctrine via improving missile defense. This is destabilizing. Politically, PRC won't discuss arms control unless US willing to discuss missile defense (scaling back), which US can't due to domestic politics. So to reestablish MAD balance PRC has to build more nukes and fractional orbital bombardment capability to circumvent US missile defense. It's attempt to rebalance not destabilize. This is also just default arms race behavior. Pour 100s of billions on missile defense and PRC (and Russia, and even North Korea) has to respond in kind. The other driving factor is nuclear proliferation, US missile defense was developed for states like NK with limited strike capabilities, but the end result is everyone else has to rebalance.