Manchuria is the leading industrial center because

Manchuria was a leading industrial center because it was part of a major Silk Route to the world.

Silk Road in Sumur, India, Asia was a trade route to many countries like China, Southern Manchuria, and Japan.

The Manchuria most parts of China provides us, being one of the most Chinese regions where heavy industries are concentrated due to the presence of the largest reserves of coal, as the steel industry is concentrated too in Manchuria