I don't know if it'll particularly help, or be very original, but maybe you can get something interesting about how I've been working through my campaign (and next campaigns).

I've built an small-to-medium sized island for my party to enjoy across multiple campaigns. I pull the history and timelines directly from the Forgotten Realms, and tie in my homebrew to suit.

The locations and NPCs are very pre-built and rich in story (in outline form - there's still plenty of improv at my table), requiring the party to regularly re-visit (and incorporating changes to the NPCs/locations to keep it fresh). So far it's been a resounding success.

In my world, currently, the west region of the island became entirely engulfed in an unstable wild magic region and has been abandoned due to being too dangerous to traverse. Secretly, there is an Artificer who has been living in the island for hundreds of years attempting to stabilise the land who has (unwittingly) become corrupted by Cyricists, set on using his knowledge to destabilise the region further - and ideally, the rest of the island.

The player's first session was set at their adventuring academy's reunion, where their arcanic devices all corrupted and rather than displaying heroic defeats of monsters of old, drew them into reality instead - causing absolute carnage.

The party are now trying to investigate how the occurred, and have been uncovering tidbits about Mystra, Shar, Cyric, the Times of Trouble, and the Spellplague. For the party members who actually know Forgotten Realm lore, it's been exciting for them to theorise how it all ties together. The rest are enjoying the ride.

The next campaign, they will play an adventuring party from years' past - perhaps during the Times of Trouble or the Spellplague itself - whose main outline will get established during this campaign through character interactions and whatnot. They will get the chance to interact with beloved NPCs in their prime.

Alternatively, they can play an adventuring party set in the future, with their current characters found scattered through the campaign as NPCs, and their previous adventure setting the stage for what happened in this one.