WoW was just such a massive phenomenon (and still is, tbh), basically everyone at least knew about it, and for so many people it basically became more of a second life than second life (old people joke), massively changing the life of these people (me being a part of it). It was basically the place where social outcasts could be social, which was huge. For me, and many others, it was all the friends they had.
The first one was maybe weird because it was still setting itself up. The second one was indeed a filler and the worst of the series (but nowhere near MMBN4-level bad). The third one on the other hand is easily a masterpiece beating MMBN6.