You aren't insured for $650M in a bank account
But even then, if you store $650 MM in a Bank of America account, that money is protected against being stolen by BOA's anti-fraud software, laws, the trillions of dollars of assets BOA has.
And that shows the difference in how each is protected.
If A has a TV, B steals the TV and sells it to C, who sells it to D...then the TV is still returned to A, and D is out of luck.
It protects again bank failure. If the one's assets are drained from the bank, as long as the bank has not failed, it will have to make the account holder whole.
That's why a company would be stupid to hold $200M at Podunk Bank of Littletown, KS but is perfectly fine to hold it in a DDA account at Bank of America, Citi or Chase