Atomic Wallet is a large non-custodial crypto wallet; that is, the key to its assets remains with the consumer, but the news of its hack has set the crypto world on fire.
All About Crypto
Crypto itself is not software; it is a complex mathematical code present in the blockchain. This code can be accessed as information in any address on the blockchain, which is called a transaction, and access to this code is a unique list of 12 words that is key to that address.

Is Wallet Hacking Possible?
Wallets are only software, and crypto exists only in the blockchain. Access to the crypto is the key, and the holder of the key is able to even import or export the addresses from one wallet (software) to another wallet. Hence, there is no possibility of a wallet hack.
What are the chances of atomic wallet hacking?
It is possible that the atomic wallet is actually a custodial wallet, like a centralised exchange. It is also possible that the wallet has been compromised anyway, due to which many cryptos have been moved around. But whatever the reason, the investigation is still ongoing, and hacking analysts are trying to help people get their crypto back.