I'm not a finance expert. But isn't the lender already making money on the mortgage by charging interest? That's the whole reason they can even sell the mortgag

I'm not a finance expert. But isn't the lender already making money on the mortgage by charging interest? That's the whole reason they can even sell the mortgage, right? Why would anyone buy a mortgage otherwise? They're purchasing a stream of interest payments, like a bond. I think that's how mortgages were before the 1970s. The bank lent some money and accepted the payments. They didn't sell the mortgage to anyone. Selling and securitizing mortgages is how 2008 happened. Maybe the old system was better in that way. Again I'm not an expert, so I don't know the side-effects of doing that.