From what I have read, the Batdickery thing is actually a relatively new phenomenon. We all knew who the Pre-Crisis DICK (all-caps because his dickery warrants it) was. Batman was reimagined as being darker Post-Crisis, and that is a perfectly logical step to take. He was becoming darker in the seventies and eighties as it was, so the initial jump was both understandable and logical. However, the dickery didn't really show up full blown until after Jason's death. I think that it was part of a character arc, a natural grieving process, and that Tim's assumption of the mantle was intended to rectify it. Of course, a few years later Knightfall came around. And then Contagion. And then the Cataclysm. And on and on and on. There was bound to be emotional fallout to those. Added to that was the Nineties (full stop). Added to that was the popularity of DKR, which was brilliant precisely because it was a deconstruction. It was never meant to be the standard state of affair, aped by writers who lacked both Miller's talent and his understanding of what he was doing.
Long story short (too late), it was a confluence of factors that started after COIE. There had been a few attempts made to pull him away from the brink, but they didn't take and so editorial mandated that he hit rock bottom in time for IC.
... and even the fix didn't always take.
It's really fascinating to me that the Nineties saw the character go off the rails in the comics, but provided B:tAS on the television. B:tAS is so close to perfect that it frightens me.