It's circular when money flows from A to B and then back from B to A again.

This is a series of transactions in which money flows from Google to SpaceX. There is no flow of money from SpaceX to Google. So it's not a circle.

More to the point, allegations of circular financing are about following cash. When NVIDIA invests in a company so they can buy NVIDIA chips, that raises a unique set of questions distinct from other types of conflict of interest. Affiliated parties doing business, as is the case between Google and SpaceX, has its own host of conflict-of-interest concerns. But they're distinct from those that arise in circular transactions.