What part of it? You are a bank and try to earn as much as possible with the money your customers gave you. However, states, consumers, and businesses don't inv

What part of it? You are a bank and try to earn as much as possible with the money your customers gave you. However, states, consumers, and businesses don't invest as much as they used to / don't borrow as much money. What do you do as a bank? You lower your interest rates to try to attract at least some customers. Combine that with exceptional supply due to quantitative easing and you have what you have right now