The Midrash (Yalkut Shimoni 2:221) explains that Navos was gifted with an especially pleasant voice, with which he used to delight the Olei ha'Regel by leading them in prayer and in praise to Hash-m. One year, he refused to join the Aliyah l'Regel and to share his talents with the rest of the nation. We know that when one fulfills the Mitzvah of Aliyah l'Regel, "Nobody will covet your land" (Shemos 34:24). The year that Navos callously ignored the Mitzvah, Achav coveted his vineyard (which eventually brought about Navos' death).

The wording of the Midrash implies that Navos' death was a result of his not coming to Aliyah l'Regel. Why, indeed, didn't Navos come? The Midrash (Koheles Raba 5:12) implies that his death was brought about by his wealth; it may be that it was in order to prevent the king from seizing his vine during his absence that he stayed behind!

Is ignoring the Mitzvah of Aliyah l'Regel a capital offense? Not necessarily, but Chazal tell us that more merit is necessary to protect a person from the evil plottings of other people than is needed to protect him from naturally occurring events (see Mar'eh Kohen to Shabbos 22a, citing Zohar). Navos did not merit Divine assistance to be saved from the hands of Achav after arousing his jealousy.

Best wishes,

Mordecai Kornfeld