I don't know if it's a bug, a feature or what, so I ask.
At turn 18, after having defeated the Beastmen and conquered their last settlement, the entire Middeland (myself) turned to Nurgle (with consequent war declaration from the entire Empire and "Game Over" at turn 25 after a crusade).
Why? I suppose that this was caused by having too many non-believers in my cities (between 20 to 40% in every city), am I right?