What can cause a user to suddenly lose a lot of reputation? I had 4415 reputation one day, and the next day I was suddenly at 2585. How is that possible?
Well, your reputation graph is suspicious
Are you sure you haven't been upvoting your stuff with another account (that also belongs to you?)
Alternatively, what does this link report to you?
I don't know what the moderators seized upon (they have hidden data like IP addresses, upvote/downvote by users etc) but these stats show clearly the effect of your Admirers.
Users like Rex and Michael Stum, Bjørn Furuknap, Lars Fastrup etc etc, get high avg scores but look at the variation (StdDev) - some get loads of upvotes, some not so much.
Your scores Standard Deviation is tiny in comparison - i.e. each and every answer gets a very consistent number of upvotes.
Totally against the usual stack overflow voting pattern.