Which negotiation went wrong? What happened exactly?

Which investment of Lehman Brothers became a disaster? Lehman was investing in what kind of assets exactly?

How come the real estate sector collapsed so drastically in a span of a few days? How did it happen?

How come people lost their homes due to subprime and why people were not able to buy new homes even if the real estate market was down to its bottom levels as houses were available for sale at a very low price?

The world went into recession due to Lehman Brothers and the subprime crisis, but where exactly has the money has gone? How suddenly has money disappeared from the world economy?

https://www.investopedia.com/articles/economics/09/lehman-brothers-collapse.asp

https://en.wikipedia.org/wiki/Bankruptcy_of_Lehman_Brothers

https://www.britannica.com/event/bankruptcy-of-Lehman-Brothers