China probably just didn't see as much value in pushing for such a person (or maybe either), combined with Russia backing a person the media/establishment found so undesirable it naturally draws attention.

Since Trump was clearly hostile to China during the whole thing and continues to be in power, if anything they likely would have pushed for a more mainline establishment person to keep the status quo. Which is the type of thing which doesn't generate nearly as much noise. It's only a problem when it's a problem, otherwise we don't hear 99% of what the NSA et al collects regarding nation state hacking.

Plus most of this stuff regarding Australia sounds like collection for predictive and intelligence analysis purposes, not directly engaging via spending a couple million on FB/Twitter ads.

Additionally tapping into private data feeds purely for collection can't be as easily spun into "hacking the election" headlines.

Otherwise China's "50 cent party" is quite well known from well before any of this election stuff and they seem to be focused mostly on astroturfing Chinese issues. Which again isnt as newsworthy as buying some politically taboo advertisements on Facebook. https://en.m.wikipedia.org/wiki/50_Cent_Party