The big miners are dumping their coins, to pay for electricity costs.
more specifically, they're shorting. this is what conventional metal miners and farmers do as well. in fact, it's the whole reason physically settled futures markets exist at all---so producers can lock in prices that cover their costs, even if it means missing speculative gains.
smart miners have definitely been hedging their operations by shorting over the past 6-12 months.
Also, too many altcoins, which are dragging the price down. Most altcoins are scams, but nobody cares in turning them illegal, governments only focus in bitcoin.
It became a snowball.
i think it's typical market deflation. scams or not, altcoins helped to pump the market up. now they're dragging it down.