because there are some people that want to collect bitcoin with cheaper price. as soon as they decide that they bought enough and fullfilled their wallets then a new bull run is going to start till they want to cash out.
It's not only that there are variety of reasons why bitcoin's price is rapidly going down, an example is the prohibition of bitcoin in some countries.
It is mere manipulation and whales now have more confidence in the space grow than ever before, I also have the feeling is demanded for some bitcoin decision/consideration. They are ready to spend as much as possible because the lower it gets the higher their profits.