Source on that? Of all the circumstances leading up to their demise, first I’ve heard of what you’re claiming here. Mostly it was they got greedy on long term bonds when rates were zero or near zero, didn’t keep the correct proportion of shorter term bonds, then the fed stopped QE and went QT, putting their bond portfolio underwater when it didn’t have to be. Had they sought more shorter term bonds that would have given them lower returns but at least the liquidity to handle the bank run, they wouldn’t have had to eat shit selling “held to maturity” bonds at a massive realized loss. Where did you read that mbs had anything to do with their shite portfolio and risk management?