The sins of Israel had grown too heavy for the patience of the Holy One. The prophet Jeremiah had warned for decades and had been ignored, mocked, thrown into a pit. A time came when his prayers could no longer stay the verdict.
So long as Jeremiah remained in the city and prayed for mercy upon it, the rabbis taught, the verdict was suspended. His presence was a shield. But the people would not listen, and the shield had become thinner than parchment. Jeremiah left Jerusalem and traveled south into the territory of Benjamin, his own tribal portion. He did not abandon the people. He was withdrawn.
While he was absent, Nebuchadnezzar of Babylon moved. He laid waste the land of Israel. He broke down the walls of Jerusalem. His men entered the Temple that Solomon had built, stripped its ornaments, took its vessels for their own treasuries, and then set what remained to the torch. Nebuchadnezzar himself did not walk the streets of the burning city. He stayed at Riblah, far to the north, and sent his captain Nebuzaradan to do the work (Jeremiah 39:9, 2 Kings 25).
The midrashic tradition reads this absence pointedly. A prophet's prayer is not a flourish on top of Jewish history. It is a structural beam. Withdraw the beam and the building falls. Jeremiah did not cause the destruction. He simply stopped being there to prevent it. The distinction is small and crushing.