Apple's Private Cloud Compute is on racks of M4 chips which have NPUs and GPUs on-die and unified memory access to however much RAM they want to put on them. All of a sudden they're competitive with NVIDIA, but they don't let anyone else use that platform.
Apple has no interconnect technology comparable to what Nvidia ships to datacenters. The larger Nvidia clusters measure their addressable memory in terabytes, the value of Unified Memory at that scale is practically negligible (if not wasted bandwidth).
You're making some pretty handwavy generalizations here without a solid grasp on why Nvidia dominates GPGPU compute.
