Panic selling and FOMO is the main reason why they lose so much, if they don't want to lose they should have hold for a long time until they get the right price of the market to sell it. And also if they do know how to diversify their investment they shouldn't lost that much. There are times that the market would stay low for a very long period of time and this is what we are experiencing today.
You seems to be right but I can assure you that is not every person that make loses were through panic sell or FOMO as you said because the power of making profit in crypto currency trading or investment are knowledge and the right timing. Do you the numbers of newbie which were prey with this current market due to lack of knowledge and not mention those the enter the market at the wrong time.