Blue
Ravenous Bugblatter Beast of Traal
I think you might be confusing the Forgotten Realms with D&D as a whole. Yes, FR did have events. But FR wasn't the default setting for any edition prior to 5th. There is no event mandated by an edition change across all settings or even that edition's default setting. The fact that FR decided to do it has to do with FR, not D&D as a whole.You could, but D&D actually have a timeline, and every edition starts and ends with a major event that changes the shape of the settings as a whole. I think the Time of Troubles ended 1st edition and started 2nd. Vecna becoming a greater God ended 2nd edition and started 3rd. Mystra's death and the spell plague started 4th, and her resurrection started 5th.
4e's default setting was Nentir Vale / Points-of-Light. 3ed's was officially Greyhawk, which was pretty weakly coupled. Want to go back to pre AD&D you get Mystara.
Source: Dungeons & Dragons campaign settings - Wikipedia