Beijing doesn’t necessarily want an Iranian victory. Ideally, it would like the conflict to drain US resources, preserve a weakened Tehran regime, and protect Chinese regional economic interests
Some may argue, Beijing is deliberately manufacturing a quagmire for US. The deeper insight is this: China is free-riding on US military’s provision of security in Persian Gulf and Red Sea, securing Beijing’s sea trade with Gulf countries, but it’s doing just enough to keep Washington’s resources bogged down. Covert support for Houthis, or Iran’s IRGC, is an example of the latter.