I'm not sure "on board" is quite the right phrase. China likely see it as a Russian-European issue, and simply haven't wanted to get involved. Putin delaying until after the Olympics (if that is what he did) at the behest of China was probably just a diplomatic move on his part: no need to antagonise China over a matter of timing, etc.
You make it seem as if China were in agreement with Putin's actions, which may not have been your intention. China have expressed the desire to see the conflict resolved via negotiation, and recently they
failed to support Russia in the UN when they were expected to vote with Russia.
So being "on board", which to me at least suggests agreement, seems somewhat of a stretch, I think.