I do not know if any one here will understand this , but I will throw it out here.

SVB took in a large amount of deposits, not out of the ordinary,as time went quickly by they could not loan enough to balance.

Someone , bank officers now gone, made the decision to buy long term bonds. As the fed RAPIDLY raised rates , to thwart inflation, the bonds value decreased.

SVB had to sell bonds at undrvalued prices to stay afloat.This quickly changed their bottom line to negative.

Also, ESG funds entered into the picture on a smaller scale . ESG Funds are money losers.

There are other factors . However, this is basically what happened. Had SVB been at 80% > 20 % ratio, in time their play on bonds would have played out but they were top

heavy to began with.