I can't honestly remember what prompted me to want to run a Ravenloft campaign. My last campaign was a very traditional D&D game (5e rules, set in the Wilderlands of High Fantasy), so Ravenloft is a departure from where I've been for a while now.
I think part of my was interested in the idea of running published modules as a way of lessening the amount of work I have to do as DM (naive, probably). We played some Ravenloft in college, I think, or at least considered running it, though I'm not sure we ever did. Al-Qadim, yes, and Dark Sun, and Shadowrun. We played a lot of that. But as Ravenloft came out around the time I was going to college, and then when I subsequently graduated and got a real job, I kind of never had a chance to really sink my teeth into the setting too much. It was always there, but kind of in the background of my life.