My theory is that when the QE rounds started and trillions of dollars were pumped into the economy (major inflationary red flag), the velocity of money dropped like a rock (major deflationary red flag) as a natural reaction.

EDIT: The reason is likely tied to the fact that interest rates sat on the bottom for the last 5-8 years and holding money was just as valuable as investing it. See the article[1] on the St. Louis Fed's website.

1. https://www.stlouisfed.org/On-The-Economy/2014/September/Wha...