Among other reasons, God did this to show that he can use imperfect men to lead his people. In fact, he has always done so.
(‏ ب )‏ لِمَ سُجِّلَتْ فِي ٱلْكِتَابِ ٱلْمُقَدَّسِ نَقَائِصُ ٱلرِّجَالِ ٱلْمُعَيَّنِينَ ؟‏