When you are trading you will face questions like this, but there are no correct answers to these questions, only assumptions. It is better to keep your mind sane by ignoring such questions.
Maybe some big investor or insitution dumped their coins, or maybe a smaller dump happened and some weak hands crashed or some negative news was published. Either way, does it really matter? Answer is No.
It sort of matters. If it was the whole collective community that decided that the bitcoin price should drop and they got out then it is a bit more long term situation, changing everyone's mind will take some time and that is why it matters. However if it was man-made (like retail ones like us are not man lol) it means that whales could end up buying it back tomorrow as well, we do not know if they will but it at least has that chance. So, if it was natural and without a proper cause than it is a long term fall but if it is whales then there is a chance for short term (and also long term as well) and that changes the way people approach to things.