Mostly because China's leadership is getting totalitarian, corrupt, ineffective, and warlike ... I've seen projections on some combo of all of the above, but really none that are even "everythings fine!" except those that have tinges of totalitarian psychology.
China isn't that cheap anymore either. They have machine tooling and economies of scale.
The US is basically in a cold war with China since they are now the principle global rival.
China's population is set to decline by a massive amount from one child policy. This combined with other supposed economic boondoggles will collapse the system.
The world learned that ultra extended supply lines aren't a good thing in COVID, and the world just seems to be going to a more chaotic era with likely lots of wars over resources, population displacement from global warming, and lots of other not-fun stuff.
Finally, the United States is becoming more isolationist. With the shrinking geopolitical importance of oil, the US might stop enforcing Pax Americana on the high seas. The primary function of the navy was to secure petroleum, and now with EVs, alt energy, and the Bakken Shale we don't need to do that for us, or the rest of the world.
