I don’t believe that nobody else would build it for them. This chip is not purely custom to Meta, as I understand it. Rather, ARM is going to be selling it to others and entering the market for “AI chips,” which is surely a market that some other ARM licensees want to be in. So therefore, ARM is competing with its other licensees, and in a potentially very lucrative, leading edge market, which is never a great place for an IP-focused company to be. Qualcomm, for instance, is undoubtedly annoyed at this.

ARM does not have their own fab, someone else is doing the actual making. ARM helped Meta design the thing.

That’s overly pedantic.

Then you’d say that Apple doesn’t make their laptops. Foxconn does.

The kind of work ARM would do to “make” a chip themselves goes beyond just design. It’s synthesis, P&R, test, packaging (generally a different company than the fab), yield management, inventory/logistics, etc.