China has already been involved quietly, funneling weapons and intel to the Russians, essentially playing the opposite role to the US. Make no mistake - this war has a component of the US and China probing each others' capabilities.

The Russians could have done this with a fishing trawler (they cut cables accidentally all the time), so like you I doubt we can infer some nefarious Chinese plot from the flag on the vessel.

I'd say another reasonable view is that China is happy to put morality aside and make money off weapons sales so long as they can get away with it.