We in US sanction 7 Chinese groups who support Military supercomputers.Likely we do same here.D'u think sanction is cause they trade with us?

We do use supercomputers. They are used for lots of things. One of which is simulating nuclear explosions. That's why there's no need for testing nuclear bombs any more. The Chinese already have nuclear bombs anyway. But we don't want them to build better ones. On April 15, 2020 U.S. officials said China may have conducted low-yield nuclear weapon tests in its Lop Nur test site.

It is more likely the other uses of supercomputers. To make other technology better. The US is already attacking Huawei for developing 5G. The Chinese are taking over the US in technology that is very profitable. The US wants to develop its own 5G and has forced its allies to abandon using Huawei technology.

The result of this is that the Chinese will have to make their own semiconductors. They can throw vast amounts of money and engineers on the problem. Or they could go straight to quantum computing.

2019, (EX)POTUS Trump, “We cannot allow any other country to out-compete the United States in this powerful industry of the future. We are leading by so much in so many different industries of that type, and we just can’t let that happen. The race to 5G is a race America must win.”
2020, sanctions against Huawei.
2021, sanctions for supercomputers.