review on "Greed, Fraud & Ignorance: A Subprime Insider's Look at the Mortgage Collapse"

About a week ago I read a book about subprime mortgage crisis in the US. The title of the book is "Greed, Fraud & Ignorance: A Subprime Insider's Look at the Mortgage Collapse". I am not a professional in finance or economics, but I can understand what the book said. I just jolt down some notes about the book.

1. The essence of subprime mortgage is no bad
In its inception, subprime was targeted for those less creditworthy to have a home and there was nothing wrong in itself. On the contrary, it helped many Americans realize their dream of a home.

2. The roles of subprime industry
The main players in subprime industry are borrower, house broker, lender, investor, rating company. The borrower submitted materials to house broker and initiated a loan. The house broker acted as a middle man between the borrower and the lender but didn't take responsible for anything in loan application. The lender was supposed to check applications and determine whether or not lend money to borrowers. When securities came in, conditions got a bit complicated. The lender packaged some loans together and attempted to sell it as some kind of mortgage securities. The rating company rated securities. The investors bought this kind of securities according to its rating. The investors were expected to reap the repaid money from borrowers.

3. Problems
(1) One of the most important problems is the very low borrowing cost, which indirectly encouraged many people with bad credit history to apply loans. The practice of zero down payment is no good.
(2) Another problem is that the house broker were not well regulated so that they always tended to help borrowers do fraud in application in purpose of making as much profit as possible without thinking that fraud may harm borrowers or lenders.
(3) The rating agency had more power than it should have. The profits of rating companies is only related with the volume but not the quality of loans. This is the incentive of rating companies to tend to rate mortgage securities higher to attract more securities into the market.
(4) Maybe the above problems is just what we saw but not why it happened. If the origin of the problem is to be probed, economical policies of the past should be examined. One argument is that the long-term low interest rate led to the financial turmoil. I'm not sure about it. Some other arguments are about the long-term industrial policy such as the repeal of Glass-Steagall Act and the legislation of Financial Services Modernization Act.

4. Solution
(1) Increasing the cost of borrowing money by any means
(2) More strong regulation of the house brokers and rating agencies

5. Question
I'm not sure how the restoration of Glass-Steagall Act would take effect in mitigating the high-leveraged impact of financial derivatives.