Bitcoin market is highly manipulated, eagle eye of big investors will not going to miss the opportunity to buy at lowest, and by observing the current market after around 55-60% price drop from $20k to $8.5k, i think this is the point whales were looking for.
It's evident that there's definitely a huge level of price manipulation, it's always the small guys who lose out in these circumstances, even the sensible investors will all have a stoploss at some point, especially those who invested at a price higher than the current 8.5k price. This crash will last for as long as it can be pushed, if the powers that be decide they can push it down to 5k or lower then they'll keep going. The only thing is, there should come a point at which the whales realise they're doing more harm than good. It's only an effective strategy if they can push the price back up in the future.