"why would they sell now when their predictions appear to materialize?"
Because of the pain of holding on for so long while experiencing a negative return. They are actually VERY happy to sell here and "get out even".
The typical investor sells winners and holds losers. Yes. The sale of the winner makes him "right" while (in his mind) the losing play is only a loser "on paper" till he sells. So he doesnt.
This behavioral finance link explains this "loss realization" dynamic very well.
http://loss-realization.behaviouralf...net/LoMa00.pdf
Here is the behavioral finance home page where this article is listed under "Loss Realization"
http://www.behaviouralfinance.net/