Celsius is a centralized custodian, not a blockchain. Anybody can build a company that uses the blockchain technology and accept funds into their USD bank accounts, and after entering insolvency, be unable to pay their creditors.

The DAO is a more interesting scenario. Users deposited into a smart contract that had a bug. This happens often in DeFi - see all the recent bridge hacks. The difference with the DAO is that the users were able to withdraw their assets because of a blockchain hard fork.