When you consider how much money whales have to play with, and how little %% institutional investors are accustomed to calling a healthy profit, ...you better believe that there will be massive selling every time BTC just shoots up 15+% like this and then shows any sign of slowing/reversing. 15% of a million dollar whale YOLO buy or a hedge fund is $150K. BTC only took 2d14h to hit 15% from 18500. If you could make that kind of money this easily, you just wouldn't need to "be greedy" and hope for it to go up even more. Of course you'd sell.
So, what's left are the small-time retail buyers and HODLers who merely want to accumulate another $10 or $100 every time it drops below $20K. And that's probably not enough support to keep BTC above 21K over a weekend.
I'm terrible at financial advice though, so don't listen to me.