I think the people in the Chinese labs have a different set of motivations, beliefs, and values that make them more amenable to sharing AI as a common good rather than some economical advantage. I've heard that workers in the Chinese labs share far more knowledge between themselves, and the narrative around AI in China is different from what we see in the USA. So it is possible, I believe, that the labs are to some extent releasing open models "for the good of humanity", or at least they believe it is the right thing to do.
Going open weights is an easy way to gain mindshare in this sort of environment, which is exactly why Meta also went open weight. The difference is that in China you had leading models going open weight which puts a lot of downward pressure on other orgs to do the exact same. I doubt China's grand vision extends beyond achieving the best system possible, and fostering a highly competitive environment is exactly how you achieve that.
The fact that open weight frontier models may also cause the investment bubble in the US to burst is likely incidental. AI funding is a bubble, and it's going to burst. The exact final cause is again mostly just incidental. The economic damage this will cause in the US will also cause substantial downstream damage to China as well, and they generally aren't so big on the whole punch yourself in the face because you don't like another country, that has become trendy in the West. So the idea of a secret economic attack doesn't even make much sense. In the status quo China wins, so they don't even have any motivation to cause chaos.
IMO because they speed-ran it so much (raising orders of magnitudes more, pushing out new stuff orders of magnitudes faster) it will also lead to the rest of the world catching up faster and shrinking the pool of people internal to them who continually benefit compared to what actually went on with IBM. There's only so much upside when you join a company with hundreds-of-billions valuation.
I guess the other part of their business plan bet was "become literal god of AGI". Maybe it'll still happen!
That only lasts until the AGI decides their god would be more useful if turned into paperclips.
Parallels to the US auto industry not paying attention to its buyers and the right strategies when they lost technical dominance to other countries a few decades back.