Fan theories are a reading practice, and they mostly survive being proved wrong

Most explanations of fan theories stop at the point where it starts to matter. This one carries on.

What theorising is actually doing

A fan theory takes elements a story has left unexplained and proposes a structure that would account for all of them at once. This is ordinary interpretive work and differs from academic reading mainly in its enthusiasm and its willingness to be specific.

It requires close attention to detail, since a theory has to survive everything the text has already established. That attention is the valuable part, and it persists whether or not the proposed structure turns out to be correct. Treating the activity purely as prediction misses that the reading happens regardless of the outcome.

Gaps are the raw material

Theorising clusters wherever a story has left something open, which makes the distribution of theories a decent map of a work's unresolved areas. Those gaps are sometimes deliberate and sometimes the result of production circumstances that had nothing to do with intention.

Audiences cannot distinguish between the two from outside, so both attract the same kind of elaborate attention. This produces the recurring situation where an accidental inconsistency generates more theorising than anything planned. Writers find this bewildering and it is a fairly logical response to a gap that looks identical to a deliberate one.

Confirmation ends things

A theory that gets confirmed stops being a theory and becomes a fact, at which point the activity around it stops. This means the reward for being right is the end of the thing that was enjoyable, which is a genuinely odd incentive. Communities often notice this and continue elaborating past confirmation, moving on to consequences rather than causes.

Theories that are never resolved can sustain a community for years, which is why unfinished works generate so much of this. The value is in the sustained attention rather than in the eventual answer.

Pressure on the work

Widespread theorising creates a difficult position for anyone still making the thing, since a predicted outcome loses its impact. Some productions respond by avoiding the predicted route, which can push a story toward something less coherent for the sake of surprise. Others proceed as planned and accept that a proportion of the audience saw it coming, which is generally the better outcome.

The audience is very large and someone will predict almost anything, so treating prediction as failure sets an impossible standard.

Inevitability was always more valuable than surprise, and theorising mainly threatens the less valuable of the two.

Where it goes wrong

Theorising becomes unpleasant when a community treats a preferred theory as an entitlement rather than as a reading. At that point an outcome that contradicts it is experienced as a broken promise, which is not something the work ever made. This is more common where a theory has become identity-forming for a group, since abandoning it then costs standing.

Communities with a healthy relationship to this tend to hold theories lightly and enjoy being wrong in public. That norm is what separates a fandom that is fun to be in from one that is not.

What survives afterwards

Long after specific theories are settled, the shared vocabulary and reference points they generated remain in use. A community that has theorised extensively can discuss a work with a precision that a casual audience cannot approach.

That precision is genuinely useful and is the durable output of an activity usually described as frivolous. It also produces excellent introductions for newcomers, since the arguments have already located everything interesting. The theories were never really the point, and the attention they required was.

The takeaway

Where a fandom theorises is where the story left a gap, deliberate or otherwise.

Popularity and craft are two different measurements, and both of them are real.