because of the bots and stop losses of the panicky traders who place them in a way to "panic sell" automatically when there is a drop starting.
Consensus drops the markets, everybody wants to imagine whales that dictate markets and secret smokey back rooms full of people who arrange the price. Every whale has to live in the ocean, with tides and waves and natural effects that swamp even the largest of players. Bigger then every group of BTC traders is market consensus, what could focus us right now is easily this 10k figure.
Personally I dont rate 10k as a big deal but certainly its a round number, a switch from 4 to 5 numbers and in perception it appears as enough of a bump in peoples brains to have a wide range of people setting their orders and stop loss sells to around 10k. Perhaps some clever soul realised they could trigger a waterfall by pushing on these collected sell orders at just below 10k, I dont know exactly but it doesnt really matter as it was the people in their anticipation not the few who moved the price in all likelihood.
I'd call out the weekend setting for this move as significant and I think we need to repeat what was done on the weekend, also we see working week traders and volume work through these prices and decide direction. This isnt that big of a deal just yet, likely I still expect we are pinned near here for the halvening event.