Everyone has its aim price especially those who trade regularly, there's someone who will sell no matter what's the situation is. For those who panic sell, sometimes its related to the current news, on what we can see on twitter, socmed and frauds. But I see no reason why would someone will think btc price will go to zero, not unless of you're craig.
You are right, everyone sets a certain goal for themselves. When Bitcoin goes up, some people who feel profitable will sell anytime they want. There are also some panicking, who think bitcoin could drop at any moment. This is possible because the whole world is going through the covid19 pandemic that has caused a severe economic crisis. Bitcoin may be affected. Their worries are well-founded. I myself do not know what the future holds, hope everything will be better.