I think, not all sales can be said something stupid. even if the price is low, somebody can sell their bitcoin, because they have speculation that the price will still fall in the time to come. and it could be someone who sells, maybe they want to earn income from trading and they have to sell their coin deposits. and they take advantage of existing market circumstances to earn income. I think everyone has their own strategies and speculation, selling Bitcoin can not be a stupid decision, everyone wants to make a profit and prevent losing too much, selling can be one strategy to earn money to start a new trade, so it really depending on how each user's point of view.