And it didn't take off until the second year, when Apple decided to open it up to Windows users (the first iPod was a Mac exclusive).
True, but I think that was a combination of several things. First, Jobs wanted to draw attention to the Mac platform, and having it be exclusive to the Mac, at least for a time, helped with the "Switcher" campaign launched in the summer of 2002. Second, and more important, the iPod was put together very quickly (according to the Macworld article, Apple hired a consultant in February 2001, had a very rough prototype in April, and started shipping in November 2001). Apple didn't have the capacity to build very many (or the desire) since it was new and untested ground for the company, and the industry. Apple worked out the kinks the first time around and then quickly improved upon it. Third, it needed Firewire since USB 2.0 wasn't common back then and USB 1.1 was too slow. Few Windows PCs had Firewire, so it wasn't until a USB 2.0 version was available that it could be usable by the Windows crowd.