The thing that made Lehman Brothers Lehman Brothers was not that they had a bad business model (the article says so much). It was that they were a central player in a network of financial products that were poorly understood that redistributed risk in a way even less understood. So when the music stopped markets froze because nobody knew who was solvent and who wasn't.

Hard to see what the equivalent in the OpenAI scenario is. Presumably when the music stops a bunch of VCs lose their shirts, the three trillion companies become ordinary trillion dollar companies and silicon valley moves on to look for the next big thing. Probably way more comparable to the dotcom bust.