Makes sense. Elon overestimated Grok usage and compute demands. Anthropic massively underestimated and is likely looking in every corner of the world for compute. SpaceX also wants additional revenue on the books for IPO.
It would have been a huge black mark on the record of both if they couldn't manage to put the deal together.
There are reportedly significant additional un-deployed GPU's (which cannot be allocated) sitting in boxes in warehouses at OpenAI who doesn't have facilities or power to deploy them. But that's a separate thing.