I have no idea if it's true, but:

https://www.reddit.com/r/CryptoCurrency/comments/al4qjm/cryptopia_didnt_get_hacked_again_the_hacker_stole/

TLDR: Allegedly:
"Cryptopia didnt get hacked again, the hacker "stole Cryptopia's private keys and deleted topia's copy. "Basically using Cryptopia's address as his own."