There could be any reason at all, but nothing changes the fact that no one knows. It is a market, there will always be fluctuations between supply and demand and as long as one is greater than the other, market will always shift towards the ones with the larger levels.

There is no much real demand for bitcoin at this stage and let's face it, whatever happened in the past with all the skyrocketing of prices, are all just plain manipulations, and a way for some whales to just cash out real big. What we are seeing now is just the corrective effect of it.