There is some Great Financial Crash of ‘08 revisionism going on.
Lehman Brothers was not faced with being underwater. It was just illiquid at the moment when it filed for bankruptcy in September 2008.
This does not surprise me. I have a client who was a lead account on Lehman Brothers in Japan. The company spent three years unwinding their accounts. That means selling off their assets to buyers at market prices. When the final unwinding was done Lehman Brothers in Japan and worldwide was solvent.
Lehman had more assets than liabilities. There was no reason to let them fail.
Plenty of knowledgeable people knew that at the time. The Federal Reserve just wanted to teach someone a lesson. And we all suffered.