The cause of the SpaceX explosion appears to have been loading liquid helium (used as a buffer in liquid fuel rockets) at the wrong pressure. Whether this was a technical error or a human one is still not clear.
NASA is now questioning SpaceX's plan to fuel rockets with the astronauts on board and may insist that they stick to the older pattern of boarding after fueling, even though SpaceX claims the crew abort system would have worked.
I'm a bit inclined towards NASA's point of view at this point. We should not try and eliminate risk from spaceflight, but how about doing it that way until we haven't had this happen again for a couple of years?