But how does that benefit the Chinese companies to have other firms host their models and gain profit from the inference, without having to pay the training costs? Training by itself is not profitable at all, only serving the newly trained model (inference) is.

Because Chinese firms and the CCP still want to be relevant at the forefront of frontier AI development. They want to have their own sovereign AI.

The alternative would be the EU strategy which is... nothing. They're content to just be techno-colonized by USA in China.