Why did the investment bankers think it was profitable idea to securitize bundle bad mortgage loans?

Question by Kuntree: Why did the investment bankers think it was profitable idea to securitize bundle bad mortgage loans?
First I don't understand why banks would loan money to someone with bad credit or not having the means to repay. Second I don't understand why investment companies like Bears Stearns would repurchase the loans from the banks. Securitize them and sell them as bonds. What are they learning at these prestigious business schools? How to be a licensed crook? The credit rating

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