What was the point of the Space Race between the US and the USSR? Proving who had more powerful capabilities. There doesn’t need to be any near-term profit at all. China has a lot to gain by beating US AI even if it makes no money from it. Money is such a small concern compared to the prestige and strategic benefits of being the global center of intelligence research.

To answer your question, what can China do if it wins? Become a global talent/education magnet, replacing the US, for example.

Capture all the input it gets via the APIs and use it for whatever it wants.

I.e. possibly the same thing USA is also doing, but USA is an ally in some sense so it's not quite as bad.

Triggering an AI crash which the whole US economy is dependent on.

Careful integration with robotics that will not be open, and will not get off the ground in the West because their AI industry will have long been wrecked (along with their economies.) China will already be too far ahead, and the West will have been their biggest customer for years.

On robotics, China will have export controls, and the US will be whining about them. Western kids interested in working in the technology will be going to Chinese universities, with the goal of completely immigrating and getting Chinese security clearances if they want access to the good stuff.