it's not about the population. China made portions of their area attractive to investors they just have more money now because they allow investors and companies to move there because of their cheap labor. they also invest and acquire companies and commercial lots in US.
the greatest achievement they did was when they've controlled the covid19 hence avoiding the recession too. while their economy is booming still and all else are falling apart, it's an advantage for them to push plans.
It's absolutely about population. Just about every mainstream economist agrees that the fastest way to boost GDP is increase the population. GDP growth and population are inextricably linked. China is no longer the epicenter of cheap labor, it's moved to southeast Asia. China is outsourcing to cheaper production points to fuel it's economic growth, the same as the US did previously. All developing economies eventually reach the point where cheap labor is needed to fuel growth, and China is now reaching that point, which is why production of textiles has shifted to Indonesia, Bangladesh and Vietnam, among others. What's fueling China's economic growth more than anything else is hundreds of millions of people moving into the middle class, because again, GDP is all about population size and technological advancement. No matter how technologically advanced the US is, it will not be able to compete with the sheer size of China's population, which is 4x our own.