Some academics have taken to categorizing the early Christian movement as apocalyptic/millennial. Those who have actually take Christ's death to be a moment of disconfirmation, one that shook the entire movement that believed the Kingdom was coming immediately. According to Leon Festinger, the man who wrote the guide to interpreting any apocalyptic movement, for a millennial movement to survive past the stage of disconfirmation it must fundamentally change. That means altering its conception of what the movement is about, it's beliefs about the end point, and proselytizing like crazy.
If the early Christian movement saw the death of their prophet Christ as a major disconfirmation the only way to keep their movement alive was to reinterpret death. Christ's death became necessary and worthy of celebration because he died to cleanse humanity. Then, the myth of his resurrection became the final nail in the coffin, so to speak. Victory over the force of death.
If you buy into this argument at all, it's almost necessary that death become celebrated. There was a need to turn what was an obvious failure (the death of the prophet) into a success. It's not enough for Christ to just beat death, not if Romans can just kill your prophet when they'd like. Death had to become part of the plan.