Alright, what about they know who the large holders are and are expecting a sell off from one of them. That on top of the current low volume could be enough to get a bear raid going or a temporary pull back at least? You could work out when funds will sell off as the position size has growth beyond their risk profile. Or maybe you have a tip off from a broker, that there's a large sell order from an institution going around.
One more! What if they knew or even thought an acquisition was about to happen. Even had a tip off? I did some checking into this hedge fund, back in 2015 they opened a short on a pharma company and started a big selloff. Stock bounced back fast over a couple of days then the takeover was announced. Stock rose 40% again before it was taken off the market that day. ZS Pharma it was called. Looking back at it now, just seems a bit too manipulated.