There are probably a few different kinds of people selling their coins, the first type are the ones which are panicking, they are seeing the price going down again and probably that was enough to scare them, then you have the speculators that do not really care about the health of the market and only care about the profits in their pockets and finally you have the smart investors which care about the technology and invest long term but that are moving their money to tether or fiat to protect themselves.
No profit will be received when you sell it when dipped, I personally assume those who sell when a crash is happening because they panic and they are ready to sell even though they know it will be a loss. But there are some people who have long hold and then the market crashes and at the same time he has an urgent need that requires him to have money quickly, when this is how investors and long term holders must face obstacles, he will be willing to sell even though they know consciously if that hasn't reached the expected profit.