The Rise of Herohammer
So I'm getting back into the hobby a bit after a long, long time out. When I last played, back in the tail end of 3rd edition, GW seemed to be pushing players away from armies built around epic heroes and towards relatively realistically balanced forces. Special characters in particular were generally regarded as a thing that should only really come out on special occasions - they were outright banned in tournaments, and most players I knew would have regarded using them in even casual games as a bit of a liberty unless we were trying to tell a specific story (eg Yarrick v Ghaz would have been perfectly acceptable if we were playing an Armageddon themed game).
Now the pendulum seems to have swung very much the other way. Running special characters seems to be not only the norm even in competitive play, but seems to be pretty necessary to make most armies competitive at the highest level. This includes things that are (to my eyes) conceptually ridiculous - like Abaddon and Huron teaming up to lead a force of about twenty marines, or Guilliman and Calgar together leading similar numbers. In the old days, even if the rules allowed it, that would have been regarded as 'dead beardy', as we used to say (I'm assuming that term has not survived), and earned you a public shaming. Even some of the armies that dodge the special character proliferation fall under this umbrella - three demon princes in one army?
This is presumably a policy decision that's been made somewhere, and I assume the key event was tournaments allowing special characters - when and how did it all go down?
To quote Community: I'm not mad, I just wanna know what happened.
TL/DR: when did special characters become so ubiquitous?