I've been with dope since the 130sat range but my guess would be mainly because you can't buy into smoke with dope.  Most of the people that want dope to do well and think smoke exchange will help are already real dope supporters but mainly hold dope.  Therefore in able to participate in the ICO they need to sell their dope in order to buy Ethereum in order to participate.  There could also be the belief that since the developers are focusing on Smoke Exchange instead of DOPE at the moment although it should benefit dope in the long run the smoke token probably has a higher chance of short term gain so some people would be shifting out of Dope short term expecting a drop to probably 500 sats or a bit lower before it starts to gradually come back.  That's my idea of what's happening.