Don't underestimate the influence of developers and the tech elite jumping on a usable desktop Unix in the early 2000s. The first places I ever saw more than one or two Mac laptops in one room were developer meetups. And you know each of those influence purchasing decisions of their families and friends as a trusted source. If OS X didn't have Unix underneath I would need three hands to count the number of people I would not have told to buy a Mac because I wasn't using one and loving it at the time.