This economic recovery, both in the United States and globally, is staying stronger and more durable than what people thought. That means that profits are going to keep coming in better for longer, and that's pushing stock prices up.
Business has tons and tons of capability to spend. The longer the recovery keeps going and stock prices go up, the more and more confident business is going to become, and the more it will spend on its operations.
Without a 'depression panic,' short-term rates probably would have bottomed fairly close to where they are today. Essentially, the Fed has just now returned interest rates back to recession lows and can now 'begin' to tighten.