They aren’t
Apple is a high net worth consumer technology integrator that focuses on highest coherence user experience. They pick the most efficient stable technology, integrate it and sell the package
Apple only needs to lead in precisely that they don’t need to lead in literally anything else
in fact if they tried to lead in those other things they would give up their integration capacity
The vertical integration argument relies on Apple having a good architecture for AI. First it was the ANE, which everyone (mistakenly) thought would differentiate Apple Silicon from other NPU platforms. Then everyone parroted the "unified memory" talking point without checking to see if professionals actually used it. Now people are pivoting to say the next-gen Apple GPUs will finally blow the last-gen GPGPUs out of the water. Which is good, because there are 4-year-old GPUs that beat M5 Ultra in compute efficiency.
I know that "Apple is behind" is a tough pill to swallow, but they literally have no analog to CUDA, CDNA or even TPU technology. Nvidia SOCs like Tegra prove that Apple could absolutely bring GPGPU tech to low-power hardware like the iPad and iOS without giving up any real features. Apple just refuses to invest in it.