I haven't studied QE specifically so I can't address that directly, but it might be helpful to think about what inflation is and how this behavior changes in a

I haven't studied QE specifically so I can't address that directly, but it might be helpful to think about what inflation is and how this behavior changes in a depression. Inflation is an increase in the general price level of all goods and services. The global economy left to its own devices would likely have entered a full-blown depression, and deflation usually accompanies this. The decrease in demand across the economy puts a great downward pressure on prices, this puts pressure on decreasing costs, this puts pressure on decreasing wages, and so on. You have a real threat of a deflationary spiral as demand further dries up due to people having less money to spend on goods and services. So, as a lot of economists argued, there was a significant threat of a deflationary spiral facing the economy, more than any threat of inflation getting out of control, which had already been low to begin with.