I don't having much to say about fundamentals. From a technical analysis point of view, according to EWT, a correction mostly happens in three strokes. First stroke was 20k->6k, second was a year long sideways move, this is the third one that will reach the extreme of the correction. In these terms, what we're seeing this last week is an extension of what was happening beginning of 2018; i.e. to ask why this happened is the same as to ask why the price fell from 20k.