Depending on the nature of the risk, yes, that might be enough insurance.

Bank deposit insurance is fascinating: it largely exists to prevent bank runs, which are caused by people believing they won't get their money out. Having any insurance means that people have less reason to believe there's a chance they won't get paid back, which decreases the probability of a run on the bank, which decreases the risk associated with the insurance, which decreases the amount of insurance needed.

Firstly, your link says nothing about customer deposits, it's about bank derivative holdings. Which aren't insured by FDIC.

But, yes, because it's pretty unlikely that all banks will fail at once, it's not necessary for the FDIC to have on hand a sum matching all insured US bank deposits.

There are also limits on coverage. If you keep $1 million in your savings account, you won't get all of it if the bank goes under.