Glass Steagal kept the commercial bank speculators away from savings institution money. Repeal allowed people like Sandy to get his hands on that cash. This led to short term maximization of the bottom line for banks. Creating the demand for paper that included liar loans. Few understood the funny paper that they were buying but if you wanted to keep your job on Wall Street you better get with the program. Feds were also part of the problem as the pushed loans for people who couldn't really afford them. False demand created by liar loans drove prices and eveyone was happy. Then defaults started and it all fell apart. Tom Wolfe's
Bonfire of the Vanities hinted at what was happening on Wall Street.
Dodd Frank does nothing to solve the too big to fail issue. It actually worsens the problem as cost of compliance can not be born by smaller banks.