The other day, I didn't know how a government could securely hold Bitcoin, especially considering the risk of theft.
I now understand multi-signature agreements and how they secure a wallet. For example, you could generate three private keys, you know the first of them, entrust the second one to a custodial bank, and have your partner hold the third key.
In this setup, at least two parts are required to create a valid signature.
Multi-sig provides the security an entity or a country like El Salvador needs to hold Bitcoin.