They might have dozens of reasons, but they already did what they did.
Some of the reasons could be:
- mitigation of US AI supremacy
- Commodify AI use to push forward innovation and sell platforms to run them, e.g. if iPhone wins local intelligence, it benefits China, because China is manufacturing those phones
- talent war inside China
- soften the sentiment against China in the US
- they're just awesome people
- and many more