What if the Temples were not destroyed? We would not have a ten-week introduction to the High Holy Days. The ten weeks are broken down in unequal parts: we have three haftarot of rebuke, and we have seven haftarot of consolation. Why are there not four haftarot of rebuke? Why are there not five haftarot of rebuke? Conversely, why are there not eight or six haftarot of consolation?
The order of ten haftarot, three of rebuke and seven of consolation, was created in the Land of Israel probably no later than the fifth century c.e. By the 10th or 11th century, this cycle was accepted throughout the Jewish world. But the acceptance of the cycle doesn’t tell us anything about the rationale.
I found a reason for the rationale for the ratio of three of rebuke to seven of consolation: It takes a long time to be comforted when a person has sustained a major loss. The Jews mourned the destruction; I don’t know why there are haftarot of rebuke. In my mind, the more haftarot of consolation we recite, the more comfort we derive.
I guess the ratio of three to seven mirrors the actual history. The three haftarot represent a loss, analogous to the destruction of the Temple, and the seven haftarot of consolation represent a system of grieving, analogous to the national period of mourning at the destruction of the Temple. We cannot be comforted without a loss.