What More Has to Happen Before the Fed Concludes That This Looks Like Yet Another Failed Interest-Rate Liftoff?

If you had told the Federal Reserve at the start of last December that 2015Q4, 2016Q1, and 2016Q2 were going to come in at 0.9%, 0.8%, and 1.2%, respectively, a rational Fed would not only have not raised interest rates in December, they would have announced that they would not even think of raising interest rates until well into 2017, and they would have started looking for more things they could do that would safely boost demand.

So why is the FOMC now not cutting interest rates back to zero? I mean, what more has to happen before the balance of probabilities says that this is likely to be yet another failed liftoff of interest rates?