The details of it being on a crypto-currency are interesting but when password/passphrase/private key security is poor it doesn't really matter the medium holding the money.
If they setup some plausible 3rd party company the game studio could use and started transfers of $10k a pop it might be some time before anyone catches it.
They are going to review and flag it. You might loose few hundred thousands but not all 625m.
Recently, we had Optimistic Ethereum (by my count, ~$250 million locked up in that network) adamantly insisting that they did everything they could to warn users that transaction history would get deleted off of Etherscan.io -- trivially avoidably, no less! -- even though none of their communication channels mention it.[1]
And that they had to make a "tradeoff" in how much effort to spend on warning users, even though their volunteers are choked every day, on Discord, with users wondering where their transaction history is.
Which, of course, pales in comparison to how a hacker found a flaw that let him print infinite ETH within their network (see the main story for that thread), and the project only lives on because he was a white hat who accepted a bounty instead.
This seems like the plot of a 90's hacker movie.
So basically $600mm in a hot wallet and no one even watching it. Just wow.
They didn’t even hack the smart contract, they just compromised 4 systems holding the private keys, and there was an RPC signing function giving free access to the 5th. Good god.