My homebrew, Galovinius, came about because of a player character. I had started a campaign at the beginning of 2nd edition and we were using the Forgotten Realms. In fact, I ran them through Ruins of Adventure and then through Curse of the Azure Bonds, then several Dungeon magazine adventures. When Spelljammer was released, we were interested in using it, and unlike many campaigns, this one was completely open ended. I had threads that were running throughout, yet no real focus until we neared the end.
What I had was one character who discovered that his uncle was a god that was imprisoned by another, neither of which belonged to the established FR pantheon. I had a wizard who was a renegede red wizard. One of his adversaries was desperately trying to kill him. He's pop up periodically, fireball this guy and try to capture him. Then there were various other enemies, such as a Jokeresque wizard entity who was uber powerful and liked to mess with the party from time to time after they inadvertently freed him from an asteroid where various powers had imprisoned him. I was a highschooler during all this, so it isn't as though these ideas are fresh or new by today's standards.
At any rate, I knew that the campaign was ending because we were headed off to college, and at least one of the guys who had been with the game since the beginning wasn't going to be around any more. For that reason, I introduced the storyline that explained the uncle diety. It turned out that the character was the rightful heir to an empire on another world and his uncle had been one of the forces keeping his family in power. Now the uncle was imprisoned, the family was overthrown, and the new people in charge were petty Tiamat worshiping despots. With that, Galovinius was born. So we ended the campaign with them challenging the new rulers and the guy taking his rightful seat at the head of the empire where he belonged.
A year or so later, when I started up a new ongoing game, I'd found some new players and I still retained one of the existing players, and he wanted to stay in Galovinius but play a new character. So we did that, and eventually one of the characters there carved out his own little frontier kingdom, and then that campaign ended.
Finally, a few years later, I had mapped out the world, written up the world's history, and come up with a premise for new characters to do something epic in the same world, so I used it again. One of my players was a carry over from the second Galovinius campaign I ran and she was pretty interested in going back there.
So, my question to Gizmoduck5000 is how exactly is that a masturbatory exercise in DM railroading? The setting arose organically as part of the campaign, and it was brought back twice by popular demand.