Why is Eliyahu taken in this surprising manner, remaining alive in order to reappear many times throughout Jewish history, up until his coming as the harbinger of the redemption? Their exists a striking contrast between the image of Eliyahu that arises from Sefer Melakhim and his alternative image, which begins to be formed already at the end of in the final verses of Sefer Malakhi and continues to develop over the course of Eliyahu's many appearances during the times of the Sages and later on.  Eliyahu is kept alive in order to complete his prophetic mission.

Courtesy of the Virtual Beit Midrash, Yeshivat Har Etzion