The blunder was likely due to the authorities' lack of knowledge about cryptocurrency. The move was somewhat akin to authorities publicly posting a username and password for a criminal's bank account — though that would likely be an easier mistake to unwind.
Crypto stolen from Korean authorities after they post wallet seed phrase
When Korean authorities posted a photograph of seized cash and other items from a police raid, they included photos of cards containing crypto wallet seed phrases, which were proudly arranged on the table next to Ledger hardware wallets for the photo op. Because it only takes a seed phrase to gain control of a crypto wallet, someone who saw the press release quickly acted to move around 4 million PRTG tokens from the wallet. The tokens are notionally worth $4.9 million, although the token is not highly liquid.
- "$4.8M in crypto stolen after Korean tax agency exposes wallet seed", Bleeping Computer [archive]