At the height of the Cold War, when the U.S. and Soviet Union governments were sworn enemies and on the verge of shooting nuclear weapons at each other, U.S. and Soviet scientists collaborated openly and productively on a wide variety of subjects. Even with government funding.

It’s not unusual to expect scientists to collaborate openly across national borders despite political winds, and in fact it is desirable.

Also funding the research is one way to ensure the results are shared.

Because they are competing on a vaguely equal footing with all the other researchers around the world. Funders want published results in return for funding, and will typically give funding to the researchers that have the perceived highest chance of publishing results if given the money. This incentivises researchers to publish anything they can. It means that money gets sent to China if it looks like the Chinese researchers are likely to make good use of it and return results. That's how academia works.