All of this seems quite shaky anywhere given humanity's reliance on Taiwan remaining politically stable and secure, which is far from a given. That so much of what's necessarily for the basic building blocks of what runs modern society is concentrated in one place with a ticking timebomb nearby is quite reckless.
I think China's waiting until the US is so broke it can't raise the money to rescue Taiwan. Based on the 40T debt, 2T deficit (not counting the 1.3T mid-term election bribe) and recent bond market jitters, that could be quite soon.
The US already depleted its missile stockpile, these missiles cannot be replaced because the US needs Rare Earths. China doesn't have to wait, the US defeated itself already
The problem China has is that as long as they depend on exports, they depend on the US consumer. If the US consumer stops spending, there is nobody else to pick up the slack.