How did Dwarf Fortress become popular?
For instance in one game a dragon attacked my fort. NBD. Everyone got inside and I was planning to catch it in a cage trap. Then use it as a decoration.
However there was a group of Human traders at my Trade Depot. They decided to run over and fight the dragon. Now the dragon is running around breathing fire. Which started a forest fire. Which destroyed my wooden bridges and doors.
Completely unscripted fun, just a result of the game simulation.
Also the game manages to make you hate goblins and elves through your interactions with them.
In evil regions eyeballs grow out of the ground, blinking at passing dwarves. However cattle will happily graze on them.
If you "delve too greedily and too deep" you'll unleash horrors of the underworld.
There's just a lot of neat stuff there.
The fortress didn't last too long after that. I tried my best to clean things up, making a nice new dining hall and brewery, but the remaining dwarves took it pretty hard - one of them ended up losing his mind while drunk and slaughtered most of the rest in the great dining hall, the rest died of disease because nobody wanted to clean up the mess. I was so proud of my towering (and first!) fortress, and I lost it all because of one stupid mistake, but it's definitely the most fun I've ever had losing a game.
http://dwarffortresswiki.org/index.php/Bloodline:Boatmurdere...
Also, I see Dwarf Fortress as the natural progression of programming games. As programmers, we always look to abstract away busywork. DF takes away the busywork of dungeon-building and hands it off to little applets.
Basically it became popular by word of mouth. I think the popularity of Minecraft led more people to hear about it, since Minecraft was said to be influenced by it. But as far as I know, it's always been a slow build, never went viral or became an overnight success.