Before jumping into the analysis of how/why Apple crashed 40% in the four months period between October 2012 and January 2013, I would like to make some comments about these types of postmortems in general. First, I'm only going to give my honest opinion as to the entire Apple crash which many people will not like and/or agree with. I'm not just going to say what people want to hear.
Second, there is a huge limitation in stock postmortems because investors are very naturally inclined to view things only in retrospect once an event has actually occurred. There is a tendency to evaluate past evidence from the lens of hindsight which makes it very difficult to go back and view the event given what we knew only at the time the event was taking place (and not with the knowledge of the crash in mind). If you go back to when Apple was trading at $700 a share, very few people expected the stock to decline 40% in just a matter of a few months for good reason.