Yeah for all it's land territory and natural resources China was not blessed with dino juice. This is one of the reasons why despite Stalin being very powerful after WW2 there was very little conflict between USSR and China. They chose to keep the trade going on their "internal" border and exert influences on their external border. Iran has the oil, China has the semiconductors and the tech - Russia will just work as a nice envoy between the 2 haha
I don't really think China needs Russia (so much)
Either as an envoy or otherwise, nice or nasty. China has been a long partner of Iran, at least since the Islamic revolution (1979). That largely explains why it has been ignoring American sanctions against this country. The bottom line is that, with China massively backing up Iran, the latter is not as isolated as the American establishment would want it to be. Now add to the mix the new digital yuan (with a Chinese regional currency in mind), and ask yourself whether Iran will need the US Dollar in the first place