The Trump administration has been consistently escalating retoric against the Chinese, and it's not hard to imagine the CIA/NSA/etc intentionally leaking facts to bloomberg that would make China look like a national security threat. This could even be done in a way where the security agencies don't leak anything actually false, but let the non-phds at bloomberg run wild with speculation to create a sensationalist story that's not really true. A recent WSJ article [1] has called particular attention to the Trump administration's escalating anti-Chinese rhetoric, calling it the start of a "second cold war". We know for a fact that these sorts of operations happened during the first cold war [2], so it's not at all hard to imagine they would happen now.
A false flag attack fits with all the information we have so far about the event: There's no direct evidence of the attack, and if the bloomberg article is ever proven to be false, then only a small number of security researchers (and HNers) will ever learn about the retraction. The vast majority of Americans will only remember reading about how "China hacked major US companies" and create an anti-Chinese atmosphere that will help fuel future anti-Chinese policies.
[1] https://www.wsj.com/articles/mike-pence-announces-cold-war-i...