I do not think the question should be closed, and indeed I have voted to reopen it.
Granted, it could be rephrased somewhat to make the following more obvious, but it seems to be essentially asking what the people in the story thought the explanation of a certain event was. It asks how many such explanations there were and what they were.
This is certainly an answerable question. The answer must of necessity be one of the following:
- Unknown as no such explanations are mentioned in the books or supplementary materials.
- There are X number of theories recorded in Chapters A, B, and C.
- No theories are explicitly mentioned, but analysis of Clues 1, 2, and 3 lends support to Theories 8,9, and 10.
I think this is pretty well focused, even if it allows for the possibility that there might be multiple theories that need to be accounted for. Long answers are no strangers to this site, and in a finitely defined series spanning a few thousand pages it is unlikely that there are more theories than can fit in a 30,000 character answer box.
I think the question is also not Opinion-Based, as there is an objective answer to the question. Again, perhaps it should be edited slightly to make it absolutely clear that it's not asking for you to post your own pet theories, but rather the theories of the characters in the story.