Bear with me, only my thoughts.
My hope is, that Chinas intention is to slowly and meticulously, basically under the nose of the US, even utilising its resources if possible in Chinas interest, wants to establish a framework for mutual development globally. Promoting their socialist system through their actions rather than trying to explicitly facilitate singular revolutions, which would've definitely gotten them sanctioned on Iran levels I'd imagine.

When it comes to direct support for political parties, I can imagine why China tries to stay from that, at least for now, see the mentioned sanctions.
You know how the US and its allies would misconstrue this as regime change(haha I know) and if necessary ostracise China from the rest of the planet.

And even if China would provide aid to revolutionary causes in Africa how likely would it be that they succeed in the long term without support in the region?

To clarify, I do not uncritically support China. But I have hope for them being able to break the US' global hegemony.

And if you think about it how else could capitalism ever be overthrown?