Not downplaying the achievements as they just achieved something the Soviet and Russian programs could not even at the height of their powers during the space race. But there are plenty of countries most notably Russia that have allowed China to purchase military/dual use technologies. Hardware such as advanced fighter jets, missile and rocket technology, and there’s also the huge numbers of tertiary education students who leave China for education in advanced fields before returning home for their careers. All of this will have contributed in some way to advancing China’s space flight program.

They didn’t achieve this in a vacuum, let’s not perpetuate the notion that China is isolated from the rest of the world.