It's absolutely the responsibility of financial institutions to secure their premises and systems. Banks have massive security departments, guards, access restrictions, systems to detect fraud, vaults etc. The government only gets involved once a crime is reported, not in securing facilities.
In fact, inadequately protecting their assets from mistakes or attacks can lead to SEC fines on top of losses,
If there is an attack in progress, the police will intervene, of course. But if it leads to a financial institution collapsing because all their money was in the one place and they weren't insured, then that's the fault of the bank.
In fact, inadequately protecting their assets from mistakes or attacks can lead to SEC fines on top of losses,
https://www.sec.gov/news/press-release/2013-222
If there is an attack in progress, the police will intervene, of course. But if it leads to a financial institution collapsing because all their money was in the one place and they weren't insured, then that's the fault of the bank.