How in the world the hwcker is able to withdraw the tokens out of the kucoin exchange and how he is able to sell while staying anonymous and un-tracked, their is high chance that some kucoin employee and insider is involved who made a complete strategy at every step to avoid being caught.
That's what i thought, the hacker is mostly like have an insider work with him, or maybe the insider himself is the hacker, if not then you have to questioning kucoin security. This is one of the reason why hodl on exchange are not recommended no matter how big is the exchange.