I assume you rather meant 'connections originating from IP addresses owned by Chinese companies'? It's trivial to use IP address from any place in the world, regardless of your actual location.
I mean from China. It was investigated and pretty conclusively linked. Is there a chance that it wasn't China? sure. But there were specific reasons that China would want to know what this company was working on, and it was more than just an IP address cross reference that pointed to them. Now don't conflate this as "US=good, China=bad" that isn't what Im saying here. Im saying that Chinese state sponsored hackers accessed their computer systems, with reasonably credible evidence.
I assume you rather meant 'connections originating from IP addresses owned by Chinese companies'? It's trivial to use IP address from any place in the world, regardless of your actual location.