They can replace high interest rate credit card debt with lower interest rate mortgage debt. And it will become a self-fulfilling prophecy.
The growing interface between high finance and lower-middle-class America was assumed to be good for lower-middle-class America. This new efficiency in the capital markets would allow lower-middle-class Americans to pay lower and lower interest rates on their debts.
The Big Short: Inside the Doomsday Machine by Michael Lewis
I have searched meanings for "efficiency" and even though I found the meaning of it, I couldn't understand what's the point being efficient so I might have wondered if there is different meaning to a word.
a) a situation in which a person, company, factory, etc. uses resources such as time, materials, or labour well, without wasting any (Cambridge Dictionary)
b) the quality or degree of being efficient (Merriam-Webster)