I think that a key issue in this case isn't just that Apple made a device that could be used for tracking - after all, you could engineer or buy a different tracking device from a number of vendors - but that its feasibility was massively increased due to a unique Apple asset - its network of iDevices. That is, Apple released a product that was uniquely good at tracking people due to an Apple-specific asset.

Slightly less, but still very importantly, there's the fact that by design you can't see if someone is tracking you unless you buy another Apple product, which wasn't an intrinsic engineering limitation, but just a choice that Apple made for their own profit.