Insolvent has a precise meaning in accounting. FRB was not insolvent. The book value of their bond and loan portfolio was accounted as held-to-maturity keeping it at cost value and not market value. As long as they could hold to maturity they'd be just fine.

The Fed put in a facility that was supposed to let banks borrow against their securities portfolio at their book value and not at their market value, plus on top of that there's also the discount window facility, which means FRB had plenty of access to capital to handle any withdrawals.

The FDIC is just on a power trip here. They don't _like_ that the market value of those securities is down based on the inverse relationship between yields and price. So they force killed the bank. There was ZERO need to do that, FRB could have just held the loans to maturity, and sure they'd lose some money on the interest they'd have to pay to borrow from the Feb to make up for lost deposits, but in no way were they insolvent and in need of a shut down.