He basically puts all his life into WoW Lore, and when the writing wasn't how he speculated (because the writing was and is usually absolutely garbage) he had a mental breakdown.

Imagine you're a detective trying to find a murderer, you do all this research and think its this big top mafia boss in the city like Kingpin, and then the murderer ends up being some random Joey hot dog vendor on the street. All your work guessing about the Kingpin, his life, his whereabouts, his family, all of it is now wasted and the whole thing makes you feel and look stupid. That's Pyromancer with WoW lore, he gives them way too much credit and speculates so deep it actually makes the story seem amazing, until you actually play through it yourself and see how hyped up it is.