Open sourcing is a complex decision so who knows what their calculations are.

But I'd assume that they're preparing for some sort of winner-take-all market in model quality where if they don't do anything the winner will be aggressive, hostile and American. Likely trying to push the Chinese economy back to the year 2000. If that is the starting point either the Chinese have to win the market (unlikely) or squeeze the profit out of it to make winning the market meaningless.

Publishing high quality open models is a well known tactic for profit squeezing. Being 2nd place with the same business model as the front-runner is a losing strategy in a winner-take-all market so they aren't going to bother with that. But if they can commoditize the model, their superior energy costs and likely coming chip manufacturing wave will hopefully give them a big advantage.

Radiolab did a great episode that covered the history of Chinese character computing: https://radiolab.org/podcast/wubi-effect

To summarize, in the 70s and 80s, China was facing an existential threat with their inability to access an economic accelerator (widespread computing) in their native language.

To the extent that there was serious consideration at the highest levels of converting the entire country to an alphabet-based writing system.

I'd expect they're looking at AI the same way:

We have to have access to this. Most of the frontier labs are American (or European). Therefore we need a solution we have continued access to.

Open weights feels simultaneously Chinese in nature (progress through making a design copyable and improvable by a large number of people) and economic (providing an incentive for the world to use Chinese models over other frontier).