משך חכמה — חטאנו והעפלנו

Q — Why didn't Israel's teshuvah ("חטאנו") save the מעפילים from defeat by Amalek and the Canaani?

A — It was not תשובת המשקל — true תשובה. It came only AFTER the meraglim died in the מגפה and Yehoshua and Calev alone survived; it was תשובה מיראה, not מאהבה. תשובה מיראה heals "מכאן והלאה" but does not uproot the sin retroactively, so it secured general kapparah (the מן and the ענן continued) but could not generate נסים specifically against the very threat they had sinned by fearing — Amalek and the Canaani — so they fell naturally by the sword.