There is no room within the mishkan for such passionate outbursts of anger. In sharp contrast to the argumentative tone of the emotional outburst which led to the plague, the complaint which followed is a pathetic whimper. After the plague, they finally understood the severity of their situation. They realized that the plague was not a punishment for sin, but a result of the total breakdown of barriers which they had brought upon themselves. After initially identifying with Korach's campaign and rejecting the barriers separating the sanctuary from the nation, the people are now ready to appreciate why division is necessary.
Sanctity demands separation, a departure from the mundane.
Frailties typical of the human condition are incommensurate with holiness. Normal societal conditions are replete with passion and competition, arguments and jealousy. Although these are unavoidable within a normal national framework, they are intolerable within the presence of God. Now the time was ripe to re-introduce the institution of kehuna. They finally understood why barriers were necessary for the realization of that great vision - to become a kingdom of priests and a holy nation.