I don't know that the Intel chips were the primary cause of success, but at the time there weren't many other options. Problem with shifting to ARM is that dual-booting Windows is no longer possible (Windows on ARM maybe?), but then I don't know that many MacBook users actually care about Windows support. The real question is going to be performance and app compatibility -- if Apple can get both of those things right, the lack of an x86 CPU may be a non-issue. And Apple would love to get away from Intel CPUs and AMD/Nvidia GPUs if it can do so.
The Lack of many important software on Apple made people avoid it for a very long time until the smart move to switch to intel.
Just one example , MS Project , there is no alternative what so ever for it , and My work demands using it (and Primavera before it) ... and many other business software that Apple is lazy to convince software houses to code it for their System.
More Over , many people who wanted Apple products badly and still wanted to game on PC , but could not afford to buy two PCs , the Move to intel made People happy about it and they started Gaming on MACS and at the same time Enjoying Apple exclusive software no one can match .
Also hardware compatibility improved alot , in the past , very very very few hardware accessories were made compatible with Apple and had the Apple Logo on it. After They moved to intel , almost all hardware worked on Apple products even if there was no official support from Apple for it ... because it just works it is the same hardware .
Thunderbolt will disappear as well and will be again replaced by stupid Apple interface for sure that will make external drives AGAIN more expensive and less available from all vendors.
and I dont think ARM will beat any CPU in the high end 32-64 cores running at 3+Ghz each cores ... ARM is way behind .. they are good and compete only in low voltage market ...
The GPU department also , Apple wont be able to catch up with AMD and nvidia new GPU , their integrated Graphics is a joke compared to the dedicated cards ...