WetGeek Apple controls their entire ecosystem, top to bottom. They decide what hardware to build, what software to write, and what libraries everyone else has to use when developing for their products. This allows them to change to whatever hardware platform they want and still provide a path forward for compatibility.
Apple can do this. PC makers can't.
ARM isn't new, it's old. It's been around since the 80's. It's more or less kept up the same level of progress as x86, but does so with a completely different design emphasis. ARM is optimized for low-power operation. It wasn't until the multicore software side of things caught up (which you can really thank AMD for more than Intel), that their processors started being competitive on the desktop/server side of things. And even that is still a very long way away from becoming mainstream.
ARM suffers from a fragmented ecosystem, where every vendor has their own custom peripherals and very few partners choose to integrate ARM's in-house designs with high performance products. It also has significant issues to sort out on communicating an ARM-powered system's capabilities to the OS. X86 has ACPI which has been around in one form or another for decades. ARM mostly relies on DeviceTree which has been around for awhile now, but isn't provided by some firmware on the ARM system like ACPI which is actually part of BIOS and UEFI for x86. This extra hurdle has limited the adoption of ARM to large vendors which can afford the time and resources to deal with the intricacies of these systems. So much so, that RISC-V has tried to go straight for UEFI out of the gate to dodge the issue entirely.
Unfortunately, the issue of DeviceTree very much affects any plans a distro has in supporting ARM hardware. With the notable exception of embedded-focused distributions like Yocto or ARMbian, most Linux distros that do support ARM do so for very specific hardware platforms, most notably the Raspberry Pi. They can do this this because those boards have well-known hardware configurations they can use with DeviceTree out of the box. DeviceTrees that the RPi Foundation maintains and provides for distros to use. Other vendors rarely do this. Imagine if a distro had to ship a different DeviceTree for every single model (and hardware configuration) of laptop or desktop made by every single vendor that use ARM for their systems. It's simply too much work for anyone. Until ARM systems with UEFI are mainstream, this won't change.