Actually there are more factors than just marketing. Your PC vs Mac example is only partially correct. Marketing took Apple to the top of the heap in the mid 80s. They dominated PCs and the old IBM OS. Every grade school, high school, and university computer lab was stocked with Apples and Macs.

It was an internal breakdown at Apple and good old-fashioned computer thievery (and marketing) that later booted Windows to the top over Macs. Macs came back with their niche marketing but it has expanded slowly but surely. The niche idea is still pretty prevalent but is not the only thing sustaining them.

Mac won, then lost, and is now trying to push forward.