I think his point is that the short interest is low, therefore it's not that heavily shorted, so if the attacker was doing the hack and shorting the stock to make money on the dip, he wasn't shorting enough to make that much money. Either that, or the attacker didn't short the stock in the first place.

That would be a silly point. Puts don't even show up in the short interest and are a great way to short a stock.

They do, indirectly because market makers hedge the puts they sell by shorting the underlying.

https://www.investopedia.com/terms/d/deltagamma-hedging.asp

Not every put seller gamma hedges. And the extent to which they do depends on how ITM the option is.