The way I'm hearing it was not a failure but an unbelievable smashing success. No one expected the rocket to get to the launchpad, much less off of it. The second stage was not expected to be reached at all, it's cool that they even tried. Greatest test launch of all time. From what I've read this morning if the test flight had worked all the way it would be like man on moon levels of good.
Eh, if SpaceX had genuinely not expected the rocket to get off the launch pad, they would not have launched it.
I expect their math was something like:
95% chance of enough engines lighting to launch
90% chance of clearing launch pad
60% chance of making 60 seconds of flight
30% chance of 2nd stage separation
15% chance of re-entry
