I think this is normal, and not a strange thing, you should know that the source of bitcoin decline in the day is triggered by high sales by the end of 2017. and this long correction is not happening before. if this correction happened every years, so, i think it is bitcoin price manipulation.

whales are the ones who can control the market, but other side factors also affect the volatility and market instability of today.

no institution manipulates the price.