but why was the iPod cool in the first place? I'm sure it cant have anything to do with the massive advertising campaign where hip/cool people dancing while wearing the white earbuds...
Large scale MP3 filesharing was cool, or rather: once it hit mainstream, not having very much music available made you an exceptionally boring person. A few years earlier, this had been the exclusive privilege of professional music journalists, DJs and record store owners, and even just getting a tiny fraction of that music availability was the dominant teenage status symbol. Once access to music exploded (via p2p), that status currency went through a massive inflation cycle, before it eventually lost most of its relevance. This hyped inflation cycle is right where the iPod came in: the iPod was what made those collections portable outside of bedrooms and basements. The advertisements in the style of Len Lye's Rainbow Dance came later, expanding the market domination, not starting it.
No one buys because of ads. They buy great products that meet their needs (in this case with the best design, UI and software).
The ads tell or remind consumers those products exist, and how good they are for their needs. The ad is a trigger to a pre-existing match. The purchase decision is created by the match.
