I agree that the decline in hashrate could be a good sign as producing BTC at this prices isn't profitable anymore. That means mining equip has to be shut down, which lowers supply and results in an increasing price. Why investors forget? Easy. Put them in a nine months long bear market where they lose 2/3 of the previous high with no sign of recovery. Their emotions will overrule any memory on fundamentals, basic investment strategies (buy low, sell high; never lose money, etc) and turn 90 percent of them into whiny bears. After that a new cycle is starting with a rise.

edit: typo