There are many reasons why they might do it. Some just lose confidence in the project and some need the money for unknown reasons of course.
Live on what it means to exist and do what it is necessary for people. It is for this reason, perhaps some and sell coins. Now the price is still falling and you need to think to look for opportunities to buy the coins until the price is cheap.
By the way, when gbx will already be traded at the exchange.globitex.com ?