I'll let you in on a little secret. I pretty much pander directly to whichever audience is encouraging me the strongest. :-)

On rare occasions, I'm inspired by the story itself (and have written thousands and thousands of words in dead fandoms that only a handful of people will ever read), but mainly it's responding to a beta reader patting me on the head going "more of this please". In fact, what turned some of those dead-fandom epics into such long detailed stories were having a couple of beta readers cheering me on the whole way. (Because it doesn't really matter how many people are patting me on the head. It's more about the consistency of "good fanfic author, have a cookie, now go write more".)

And I don't really have an active beta/cheerleader at the moment, so output has been slim.