It's how they operate.
https://a-capp.msu.edu/article/a-brief-analysis-of-the-chinese-intellectual-property-regime/
Pretty easy since we exported all of the manufacturing to their country and then put secret stuff on the Internet. Hacking occurs only through Internet connectivity. Why are secrets kept on systems with outside access? Who are the stupid ones?
Many post to imply that the Chinese are not smart enough to innovate. That is what raises my hackles. Of course the CCP steals stuff, that is what nations do when they are in a hurry to achieve parity. We do exactly the same thing whenever possible, as does any other nation in the world.