The retrospectives will be interesting. In defense of CSU and the other agencies, if I had released a seasonal forecast in April or May, I would have likely predicted a very hyperactive season based on how the SSTA pattern was at the time (and also knowing the El Nino was dissipating). However, my ACE forecast model (which predicted an ACE of "only" 154 this year) was purposefully released in the first week of July, because often it's not until June that the contours of a season become apparent. This year is a good example of that, having a very favorable SSTA pattern in the Spring which was significantly disrupted by a +NAO in June. A much more dramatic flop occurred in 2013, and the opposite trend occurred in 2004. Also, the evolution of ENSO tends to be more clear by June and after the Spring barrier.
That said, CSU and TSR both released forecasts in early July and still called for an ACE of 230 and 240, respectively, so their methodologies obviously differ. It's far too early to make any definitive claims about how this season will progress or grade how anyone performed, but I'm enjoying the discussion about what is causing this long lull. Trying to understand unexpected events like this are how the science of forecasting is improved.