Here's why:
* Bore: Can be used to describe someone who is extremely tedious or dull. It can also, less commonly, refer to someone who is intensely interested in a specific topic to the point of obsession.
* Maniac: Means someone who is extremely enthusiastic or passionate about something, often to the point of being reckless or irrational. This aligns with the second definition of "bore" - someone with an intense, obsessive interest.
While the other words suggest some kind of mental instability, they don't directly relate to the idea of being intensely interested in something.
Let me know if you have any more questions!